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    "source_key": "britannica_1926",
    "source_title": "Encyclopaedia Britannica (1926)",
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    "chunk_id": "1926:ammunition:c72b1fd06f42",
    "title": "AMMUNITION",
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    "verified_text": "the normal modern shell, whether monobloc or made in parts and assembled, has the general form of a cylindrical steel body, hollow to receive the filling, with the base flat and the head pointed. i. ammunition for ordnance in designing projectiles for ordnance, it is necessary to consider the function of the shell at the objective, the capacity of the shell to withstand the forces of projection, the ballistic qualities of the projectile in flight and the suitability of the design for manufacture and supply. the design of a shell must therefore be considered as a compromise between these conilicting quali- ties, as 1t is obvious that a projectile designed solely for pur- poses of flight might prove incapable of sustaining the pressure developed in the gun. it is necessary, however, to give due consideration to all the essential properties of a shell. the head was normally of true ogival shape, with the centres of the circular arcs in or near the plane of the front end of the body and with a radius varying from about 13 to 24 calibres. the driving band was pressed into a groove near the rear end of the shell to cause rotation of the projectile, to prevent undue escape of gas around the projectile when the gun is fired, and to provide a seating for the projectile. a fuse hole was prepared either in the nose or base of the shell. range and accuracy—many experiments have been made since 1900 to improve the shape of projectiles with a view to ob- taining longer ranges and greater accuracy, with the ultimate result that modern projectiles have generally long, tapering points which correspond to an ogive of from 6 to 10 calibres. although, theoretically, there appears to be no limit to the length of the head, in practice, a head longer than that due to an ogive of 8 calibres radius has certain disadvantages affecting is the accuracy of flight. as an alternative to increasing the length of the shell itself, a device known as a false ogive, or ballistic cap, has been much employed, particularly by the germans; this consists of a light, hollow cap screwed on to the body of the shell proper, thereby improving the general shape and not substan- tially affecting the accuracy. attempts have also been made to obtain still greater ranges by stream-lining or boat tailing the base in varying degrees. a certain increase of range may thus be obtained, under certain conditions, but frequently a loss of accuracy results. the results obtained by varying the shape of projectiles depend, to a great extent, on the velocity of projection, and the effect on range anil accuracy of any shape of head is influenced by the shape of the base of the same shell and vice versa. it may be stated that modern high velocity projectiles have long, tapering heads, sharp points and parallel bases. projectiles fired at velocities lower than 2,000 ft. per sec. (f.p.s.) may also have stream-lined bases, but when the velocity falls to below 1,200 f.p.s., the head shape tends to bluntness but more attention is devoted to the shape of the base. these remarks are intended to apply merely to projectiles actually in use at present, and are not intended to define the optimum design. driving bands—vthe material generally used for driving bands is copper, in the form of rings, and no other substance appears completely satisfactory for this purpose. the chief dis- advantage of copper is that it gives rise to metallic fouling in the gun, called coppering, which can be removed-by chemical or mechanical processes, with special apparatus, but decoppering is difficult to carry out in the battery position in the field. attempts have been made to incorporate in the cartridge or attach to the shell some material which will remove the copper from the bore of the gun during firing. a shell normally has one driving band, but two or three may also be used. the germans, in large shell, normally used three bands. weight, length and diameter —other factors affecting design are the weight, length and diameter of the shell and, to a great extent, these factors are interdependent. in practice, a certain maximum weight of shell is found suitable for a definite gun, mounting and charge. the diameter is fixed, and the length therefore depends on the type of shell under consideration. there is a certain limit to the length of the shell, which is gov- erned by stability. approximately the weight of a shell in pounds suitable for a given gun is half the cube of the calibre in inches. the diameter of the shell body is slightly less than that of the bore across the bands, to ensure a free passage for the pro- jectile up the bore. the modern practice is to keep this clearance as small as possible and in some cases it is as small as 0.01 inch. afatertal—with modern ordnance, the projectiles are prac- tically all made of cast or forged steel. during the world war, cast iron was largely employed to assist in overcoming shell shortage in various countries, but its use is now generally dis- carded, except for projectiles used for practice and special pur- poses. the steel employed may be either straight carbon or alloy steel and in certain cases may be subjected to heat treat- ment. normally, modern shell are manufactured by forging from stecl ingot or bar, though in certain cases shell may be cast to the required shape. types of projectiles —projectiles for ordnance may be divided into two main classes, shot and shell. the only shot now found in modern armaments are proof shot, practice shot, paper shot and case shot. proof shot are solid shot used for proving ord- nance and charges. practice shot are solid shot used for practice purposes. paper shot are used to test gun mountings which can- not fire service projectiles in peace time, owing to their siting. they are made mainly of paper or pulp, and their weight is cal- culated to exert the same stress on the mounting as a service round, but they break up in the bore when fired. case shot gen- erally consist of three or more long steel segments held in posi- tion inside a thin, tinned canister, the whole being filled with bullets. the top and bottom are formed of steel plates and, in larger natures, the shot is stiffened by a central bolt. it is not much used in modern equipments. ii4 the natures of shell now used are: common pointed or c.p. shell; high explosive or h.e. shell; shrapnel shell; armour piercing or a.p. shell; and special shell, of kinds such as smoke, star (illumi- nating) and incendiary. c.p. sheli.—little development has taken place in c.p. shell, as such, in modern types of ammunition. filled with powder, they are still to be met with in certain countries and used with or without soft steel caps they fulfil certain functions usefully. for many pur- poses they have been superseded by h.e. shell. they have not been utilised in british service with h.e. fillings but have been amatol fic. 1.—modern british h.e. shell. developed as h.e. shell in the german naval service, in which case they have been filled with tnt, the method of filling agreeing with the usual german practice for h.f. shell. he. shetl.— modern british h.e. shell are normally of forged steel with solid bases, a special steel base plate being fitted in a recess in the base to give addled strength and prevent any possibility of ingress of gases. the walls may be comparatively thin, which gives good effect against material, or, alternatively, the walls may be thick enough to give good effect against personnel. the nose of the shell is prepared to take a fuse. in other countries solid bases are not considered essential in these shell. plug wood block felt washer pressed trotyl pellet cardboard container 4 blocks - lead king decoppering band fic. 2.—modern german i.e. shell. explosives used as shell fillings are ordinarily, picric acid, tnt ({tri-nitro-toluene), and amatol, which is a mixture of tnt and am- monium nitrate. other substances used are dinitrobenzene, trinitro- anisol and guncotton, and, during the world war, many other sub- stances were tried. the explosives are generally inert and not easily detonated, and hence an exploder system is ordinarily found between the fuse and the filling itself. in some cases, where detonation gives little or nosmoke, some smoke-producing mixture is included in filled shell to assist observation. a typical modern british h.e. shell is a ammunition tion. the filling is amatol, with a proportion of tnt to facilitate detonation. the exploder system in this particular case is repre- sented by a gaine and an exploder. fig. 2 illustrates a modern german h.e. shell evolved during the war. the filling calls for little comment. there are several points of interest in comparison with earlier shell. the base is closed by an adapter, which is contrary to british practice. three driving bands are employed and a decopper- ing ring is fitted. two fuse holes are provided, which permit of either nose or base fusing, or even the use of two fuses at the same time. this shell also provides a good example of the ballistic cap or false ogive. shrapnel.—modern shrapnel do not differ in principle from the earlier types. the walls are made as thin as is consistent with abil- ity to stand the stresses on firing and in flight. the bullets are ordinarily of lead antimony alloy, 41 to the lb. for light shrapnel, increasing in weight for heavier shell and for special purposes. they are kept in position by resin. the badly may be closed either by a fuse socket or by a separate head, the part in either case being so fuze filled powder millboard washer parachute metal lube fi/led powder steel supports leatherboarad cup paper washer asbestos tube star case pressed sections of star composition brass tube o/dered to star case stee! washer ardboard washer 8 powder pellets & 8strand quickmatch layer of friming ilfboard washer steel base container filled fowder fic. 3.—section of german 15 cm. star shell. 2? ¢ a ae = z f 9 ‘he q secured to the body of the shell that its removal is easily effected by the small bursting charge of fine grain powder. the central tube may or may not be provided with powder pellets. a.p. shell.—little change is to be seen in modern a.p. shell. an improvement in shape, by altering the shape of the cap, and the introduction of h.e. as filling instead of gunpowder are the only important changes in recent years. special shell.—gas shell were introduced by the germans during the world war, and were developed by them into weapons of great offensive power. ordinarily shell bodies of h.e. design were uti- lised and filled with a liquid or solid substance which volatilised on exposure to the air giving a concentration of gas sufficiently strong to disable an unprotected man. the shell were usually opened by a small charge of explosive, the fuse employed being of the instan- tancous type. in later patterns of shell, the chemical ingrecient was enclosed in a bottle which was buried in an ordinary h.e. filling. the shell functioned as an ordinary h.e. shell with the additional deleterious effect due to the chemical. smoke shell are really another product of the world war. in design they resemble gas shell and are filled with composition in- illustrated in fig. 1. the steel body is stout, giving good fragmenta- | tended to give smoke clouds for purposes of concealment. they are ammunition actuated by instantaneous fuses and contain small h.e. opening charges. incendiary shell, also introduced by. the germans, con- tain incendiary substances and are used with either time or per- cussion fuses. they call for no further comment. the star shell has many advantages. the latest type of illuminating shell may be con- sidered as well represented by that illustrated in fig. 3. there is a time fuse which can be sct for any time up to 33 seconds. when the fuse functions, the flash from the magazine ignites the powder in the clome of the shell and blows off the head of the shell. the flash from the powder passes clown a side channel to the powder charge in a small magazine in the base of the shell; the powder explodes and ejects the star and parachute from the body, and at the same time the star composition in its case, by means of quick match strands andl powder pellets embedded in the composition, is ignited. after ejection, the parachute itself opens and supports the star until it burns out. cartridges and ignition.—cartridges for ordnance are divided into two main classes called technically breech-loading or b.l. and quick-firing or q.f. and each class is subdivided into gun and howitzer cartridges. all modern ordnance its breech-loading and the terms b.l. and q.f. merely indicate the system of obturation, or gas sealing, employed with the gun. of recent years no radical changes have taken place in the make-up of cartridges and means of ignition, and, in principle, these stores have not varied since 1911. the world warimposed on the bellig- erents certain drastic changes in equipment owing to the lack of raw material, and these changes affected cartridges to a cer- tain extent. for the main part such changes were inferior sub- stitutions, which have disappeared. propellants —generally speaking, the propellants employed in modern cartridges are of the nitroglycerine or nitrocellulose type; the former class containing both nitroglycerine and nitro- cellulose, whereas, in the latter, nitroglycerine is absent. all these propellants, generally described as smokeless powders, are somewhat difficult to ignite, and hence an igniter is a feature of cartridges, which may be found in the form of a separate store called an igniter, or be embodied in the primer or igniting me- dium. the igniter is ordinarily composed of fine grained gun- powder. the propellant is usually manufactured in cords, sticks or tubes, which shapes are known commonly as stick forms. it is, however, also prepared in flakes, discs and other small shapes which, for want of a better name are called granular forms. well-known stick forms are cordite and rehrenpulver. well- known granular forms are nct, ballistite, ringpulver and wiirfelpulver. during the world war the germans and aus- trians were compelled to use inferior propellants owing to the scarcity of nitric acid. an example of this type of propellant is ammonpulver (see explosives). b.l. cartridges —b.l. gun cartridges are built up of bundles of propellants of stick form cut to the required length, tied with silk and inserted into cylindrical silk bags of which the ends are closed by silk discs. an igniter 1s stitched on to one or both ends of the cartridge. this type of igniter consists of fine grain powder enclosed in a circular bag of shalloon and covers the ends of the cartridge in order to intercept the flash from the igniting medium, tube or other flash initiator. the exterior of the car- tridge may be laced with silk cloth tape so as to form a stiff cartridge. the charges for heavy guns may be made up in sepa- rate portions, for convenience 1n handling and to permit the use of a reduced charge. in large cartridges a silk cloth becket runs up the centre and has a loop at the top for handling (see 1.872). granular form propellant has been used for certain cartridges and, in principle, the method of making up is similar to that employed with the stick form, with slight modifications to com- pensate for the lack of rigidity of the cartridge. b.l. howitzer cartridges are similar generally to the earlier type (see 1.873). in modern practice, bundles attached to the core by tape may be used instead of rings. qo.f. cartridges —in these cartridges, the propellant charge is contained in a brass case which effects the obturation of the gun. this class of ammunition is of two types, fixed ammunition and separate. the use of the brass case influences rapidity of fire, in that it obviates the operation of sponging out smouldering debris; it allows of the cartridge carrying its own means of igni- tion, thus saving one loading operation, and it also offers great tis safety against accidental ignition. on the other hand, the brass case 1s expensive in itself, and any defect in it may cause serious damage to the gun, the gas having to escape through a con- stricted channel; it adds to the weight of the cartridge, entailing increase in transport, and finally, where large output is required, the supply of raw material becomes a serious proposition. dur- ing the world war, the germans were compelled to use steel as a material for q.f. cases owing to the shortage of brass. the use of such cases was limited to ordnance of small calibre or ordnance with low velocities. means of ignition—b.l. cartridges are ignited by means of electrical or percussion tubes. q.f. cartridges carry their own means of ignition, which may be caps, primers or tubes, the latter being fitted with adapters. a typical modern percussion primer is illustrated in fig. 4. the body is of brass, with a tapered flange to ensure a good fit in the cartridge case, and is suitably screwthreaded. a brass cap, filled with cap composition, is brass washer liaen disc, she/laced. fowder, pressed in. fic. 4.—percussion primer. seated in the body and a brass anvil plug with central! hole screws down on to the cap. the upper portion of the primer forms a magazine which is filled with fine grain powder, and the primer is closed with a linen disc and brass washer, secured by the end of the body being turned over. the primer functions when the striker of the breech mechanism impinges on point a of the primer, the cap fires, the powder in the magazine is ignited and the subsequent flame ignites the propellant. fuses.—a fuse is employed to initiate the bursting, explosion or detonation of a shell at the required place or time. the mechanism ofa fuse must fulfil two conditions: it must operate at the required time or place and it must not operate prematurely. the latter condition is fulfilled by embodying external or internal safety devices in the design. external devices are employed when it is impracticable to provide sufficient protection by internal means. these may consist of pressure plates, safety caps or pins and similar devices intended to prevent the fuse from arming or firing before loading, during transport or storage and preliminary handling, including accidental dropping. caps and pins are removed before loading. internal devices, while performing similar functions to the external devices, also give safety during acceleration in the bore and during the period of flight, and comprise such means as safety shutters, tapes, cen- trifugal bolts, ferrules, collars, pillars, detents and springs. normally, they prevent premature collision between detonators and needles, or may prevent ignition of the bursting charge in the event of accidental firing of the detonator. the use of safety devices will be considered in connection with individual fuses described below. fuses may be classified as follows: { (a) direct action (d.a.). | (b) graze action, nose or base. (2) time, or time and f (a) composition or burning. percussion fuses | (b) mechanical or clockwork. (1) percussion fuses 1. (a) direct action fuses function as a result of a direct blow on the nose, a hammer or needle being forced on to a detonator. a later pattern of d.a. fuse is the british fuse no. 106 illus- trated in fig. 5, from which its general construction will be under- stood. it is protected before loading by a safety cap, which is removed by hand. a split steel collar is interposed between the underside of the hammer head and the top face of the fuse body and round this collar the safety tape is wound. on firing, the tape weight is gripped between the hammer head and body. when acceleration ceases, that is, when the shell leaves the bore, the weight is released, flies off, unwinds and carries the tape with it, tearing away the split collar. the hammer is then sup- ported only by a thin shearing wire. on impact, the hammer is 116 driven in, shearing the copper wire, the detonator is fired, and in turn fires the magazine. a safety shutter is provided, which only opens after the shell leaves the bore of the gun. fuse no. 106 may be taken as typical of a class of d.a. fuse which is rather more sensitive than an ordinary d.a. fuse, and is known some- times as an instantaneous, or, in german, empjindliche fuse. pellet of ce. guide pin brass jape with weight i; hl “sr steel collar in halves [aleks ‘copper shearing wire stee! washer uit shutter detonator fic. 5.—percussion direct action fuse. another type of d.a. fuse, somewhat less sensitive than the ordinary type, is the direct action impact type (d.a.i.). such fuses merely differ from ordinary d.a. type, in that the suspen- sion of the needle is very much stronger and hence the fuse requires a stronger blow on the nose in order to make it function. (b). graze fuses or check action fuses function as a result of the forward movement of a graze pellet relatively to the main body of the fuse. when the shell receives a check in velocity a pellet carrying a detonator moves forward onto a fixed needle or alternatively a needle pellet moves on to a detonator. a typical nose graze fuse is illustrated in fig. 6. the illustration represents the german fuse kz. f. spgr. m. k. and shows its creep spring, secured to pellet with solder 5 brass sately leaves split brass sleeve millboard plan showing arrangement of leaves fic. 6.—percussion graze fuse. general construction. before firing, the detonator pellet is kept away from the needle by five interlocking brass leaves held in nosition by a brass ferrule supported on a split brass sleeve. on acceleration, the ferrule sets back clear of the safety leaves and rebound is prevented by two lugs on the sleeve. when acceleration ceases, the brass leaves open out one by one under the influence of centrifugal force, leaving the fuse in a sensitive condition or “‘ armed.” creep action of the detonator pellet dur- ing flight is prevented by the so-called creep spring. on graze, the pellet flies forward on to the needle and the detonator fires, the flash passing through a hole in the pellet to the exploder in the shell. ammunition a practice common in german design is to arrange a combina- tion of direct and graze action effects in one fuse. in this type the detonator is housed in a movable pellet which functions in the usual way. the needle is formed on the inner end of a rod, the outer end of which projects from the top of the fuse. on impact, the detonator pellet moves forward on to the needle as in an ordinary graze fuse but in addition to this action the needle is also forced on to the detonator by direct action. 2. a time fuse is one which can be set to burst a shell at a cer- tain predetermined time after firing. a time and percussion fuse, commonly known as a t and p fuse embodies, in addition to the time mechanism, a graze percussion mechanism which will function independently should the shell strike any object in flight or on impact with a target. time fuses are divided into two main classes, (i) burning or composition and (6) mechanical or clockwork. the modern composition fuse is exemplified by the british t and p no. 80 (see 1.870). very little change has occurred of recent years in the design of these fuses. attempts have been made to lengthen the time of burning by increasing the number of rings and by altering the — gaps in ring steel frustum ring hand brass catch top plate —— eee ra) upturned end lever naireden = main spring spiral spring s hatchet teeth = barrel third wheel = winding wheel a slot in bottom = plate —_ © le second wheel centrifugal cif i bolt — se | a oo : - fin e ge §}.— escape wheel triker ra . ‘s hair spring ee jie ix ss siding piece betonator magazine fic. 7.—diagram illustrating action of mechanical time fuse. composition in the rings but, fundamentally, the design remains unaltered. in the t and p no. 80 fuse, the escape of gas from the burning composition is facilitated by radial gas escape holes. in some foreign designs, gas escape through the nose is arranged, but the radial method is more general. the movable ring type of fuse is almost universal but a notable exception is noted in the french type of t and p fuse no. 23-31, which is set by punching a hole at the appropriate point in a composition-filled lead tube by means of a machine called a debouchoir. the simple time fuse is rarely found in the modern armaments, a percussion mechanism being almost invariably embodied in the design. should a time fuse only be required, as in the case of anti- aircraft projectiles and star shell, an ordinary t and p fuse may be employed with its percussion mechanism removed. never- theless, fuses which are time fuses only may be found in use with various equipments. the use of burning composition in time fuses is by no means ideal, and for many years experiments have been carried out with a view to obtaining a clockwork or mechanical apparatus. various patterns were tried, but none were satisfactory until 1916 when the germans brought into use a clockwork fuse doppelziinder 16 (t and p fuse 1916 pattern) which may be considered as typical of this class. this fuse is illustrated in ammunition figs. 7 and 8, the latter illustration being merely diagrammatic and the description which follows is of principle and arrange- ment only. the clock train is driven, as in a watch, by a coiled spring in a barrel, but the escapement is original and peculiar. a straight steel spring takes the place of the hair-spring, which would be rendered useless by the effect of rotation and shock of discharge, and as the length of the straight spring 3s adjustable, the movement of the pallet of the balance, and therefore that of the escapement wheel and the clock train, is controlled and regulated. a horizontal hand, the position of which depends on the setting of the fuse, has, on its under surface, a notch, into which fits the upturned end of the lever at the top of the striker. when the clock train is started, the hand moves round with it, but is prevented from rising and releasing the lever by a ring attached to the conical housing of the fuse. this ring is pro- vided with two slots into which the hand can fit; thus, when the cap,steel dome, brass susserdg uspending sprin j clock case, pass screwed collar/| housing for locking king, crass clockwork bras 5 steel fins steel dowel pin steel wire base piece brass percussion detonator 4 flash holes maga zine aluminium bar need/e, stee/ stirrup, brass lead washer washer, brass fic, 8.—typical time and percussion mechanical clockwork fuse. clock is working, the rotation brings the hand into coincidence with the slots, and when forced up by the action of a small spring, it releases the upturned end on the lever. the striker, previous to firing, has been held in the safe position by a collar on it, which rests on a shoulder of the centrifugal bolt, but when this bolt is moved away by the rotation of the shell, the outer end of this shoulder still rests on a steel pin. when the upturned end of the lever is freed from the notch in the lower side of the hand, as previously described, it ilies out and rotates the striker, so that the collar clears the steel pin and allows the striker to fall and fire the detonator. the setting of the fuse and the hand is accomplished by turning the housing with a suitable key, this housing being free to move before firing. on discharge it is very ingeniously clamped to the body of the fuse by means of stecl pins in a ring in its under surface. this ring sets back and the pins are driven through the flange of the clock case, a groove being turned on its under side to thin the metal, and thus to allow of easy penetration. the clock train, wound up like a watch, is started at the moment of firing by the setting back of a detent. ii. ammunition for other weapons since 1gto rapid strides have been made in the development of new designs of ammunition for rifles and machine guns. the cartridge case—the general manufacture of the case has not altered except in detail, but special attention has been given to the hardening, so that, whilst the front end is left suffi- ciently soft to expand against the walls for gas sealing, the rear half of the case is left hard to stand up against the force of extraction. means of ignition—no change has been made in the cap or primer, but it has been realised that the composition may deteri- orate, especially in conditions of warm, damp storage, or in con- tact with moist powders. this leads to missfires or hangfires, 117 and slow or incomplete ignition is found to exercise a most dele- terious effect on accuracy. the tendency is, therefore, rather to overcharge with fulminate composition in manufacture, so that the efficiency of the-ignition shall not be destroyed, even though some deterioration may have taken place in the composition. charge.—it is still a debatable point whether purely nitro- cellulose powders are preferable to ones containing a proportion of nitro-glycerine. nitro-glycerine has the advantage of making the powder more powerful, bulk for bulk and also of improving the gelatinisation, making the powder damp proof and better able to withstand adverse conditions of storage. on the other hand, pure nitro-cellulose powders give the same velocities with a lower maximum pressure than nitro-glycerine powders, and are claimed by some to give more accurate shooting. in the result, britain has held to cordite, but other nations, par- ticularly the united states of america, have adopted n.c. powder as their normal load. bullets —greater changes have been made in the bullet of the small arm cartridge than in any other component part. not only has the form of the earlier bullet been materially changed, but several entirely new types have been evolved, such as the tracer and armour-piercing bullet and the normal, or service, bullet. during the last century the use of small arms at distances greater than 1,000 yards was never seriously considered, though it was realised that the actual range of these weapons was well in excess of that figure. with the gradual improvement of machine-guns and the increased care taken in teaching musketry to the infantry soldier after the boer war, it was found that massed fire could be brought to bear on large targets with great effect at long ranges. the problem of increasing the range by improving the contour of the bullet at once came to the fore, and by 1914 most countries had discarded the round-nosed bullet in favour of a pointed one, the contour of the point being struck by a circle whose radius was about 8 times the calibre. further improvement in range can be obtained by stream-lining or boat- tailing the base of the projectile, but as this involves certain difficulties in making the bullet take the rifling, the practice has not been universally adopted. as regards the make-up of serv- ice bullets the lead core with special envelope remains the standard practice, but efforts have been made to improve the material of the envelope so as to obviate fouling the bore with the metallic deposit left by cupro-nickel. in america a 90% copper envelope with 8% zinc and 2% tin has been found suc- cessful as an anti-fouler. | tracer bullets.—the value of a bullet which left a visible wake either of smoke or of flame, was recognised in the early days of air fighting during the world war. this led to the introduction of a bullet stemmed with burning composition, usually a mixture of barium salts and magnesium, in the base, which was ignited by the propellant gases on firing the rifle. the difficulty with a tracer bullet is to make it range identically with the service bullet, and the only solution so far found is to bring the two together at an optimum range, say 500 yards. armour piercing bullets —the need for combating armoured cars, aircraft, tanks and snipers’ plates with a missile having a better penctration than the service bullet, led to specially de- signed armour-piercing bullets for such purposes. these consist of jacketed bullets, having envelopes harder than those nor- mally used, to withstand the increased charges which are needed to give penetration. sometimes soft steel is used for this pur- pose. the core consists of a specially treated tool steel, and a lead surround is provided, since without this device the bullet would be too hard to take the rifling. the lead surround has the further function of supporting the point of the core at the moment of impact, thus preventing fracture of the hardened point which might otherwise occur. | armour much over 0; 25 in. cannot be penetrated by a 0-303-in. calibre bullet. on the other hand it takes a 1-in. plate to keep out a well-designed o-5-in. calibre bullet, and this thickness of armour is nearing the limit of weight that any land or air vehicle can profitably carry. for this reason every first class nation has introduced or is contemplating the introduction of a o+5-in. 118 calibre weapon with a.p. bullet for such purposes. for normal use by the infantry soldier, however, the weight that can be carried by the individual is the limiting factor, and any increase in calibre would materially reduce the number of rounds that could be taken into action. | machine gun ammitnition.—progress in machine gun ammu- nition has run on strictly parallel lines to rifle ammunition and in most cases ammunition is mutually interchangeable between the two weapons. the problems are the same and may be sum- marised as the attainment of a high standard of accuracy, a minimum of erosion, wear and metallic fouling and elimination of flash. the adoption of large calibre ammunition (0-5 in. and upwards) will affect machine guns more than ritles, since for the former the question of transport is not so formidable. pistol ammunifion.—lin the british army the 0-455-in. calibre revolver with its heavy, unjacketed lead antimony bullet has remained unchanged for 30 years. as a man-stopping projectile at point blank range it remains unbeaten, but its weight and poor accuracy at longer ranges limit its value. most nations have adopted automatic pistols for their subsidiary weapon, and for these, jacketed bullets, either of copper or cupro-nickel, are employed. the various nations differ as to optimum calibre for pistol ammunition, but the tendency appears to be away from the light comparatively high-velocity bullet such as the german 0-300 mauser which was sighted up to 1,000 yd., thus holding the pistol to its true rele, namely that of a man-stopping weapon at short range. aeroplane bombs aeroplane bombs have their inception in the indiscriminate throwing of trench grenades from the rather crude flying- machines which were in existence during the early stages of the world war. gradually bombs and bombing methods were improved till, before peace was concluded, the aero- plane bomb held an important place as an offensive weapon. the main difference between aeroplane bombs and gun pro- jectiles is one of strength. the latter may have to attain a muz- zle velocity of about 2,000 f.p.s. in the length of the piece, and this entails pressures running up to 20 tons tothesquareinch. the former is merely dropped, so that the stresses on it when falling are very little greater than those encountered in normal han- dling and transport, and it is only when penetration of concrete buildings or armoured decks is sought that anything more than a thin steel case is required to contain the i.e. filling. as regards shape, the terminal velocity of an acroplane bomb is never above 1,100 f.p.s., hence the stream-lining of the tail is just as important as the contouring of the head. most bombs are therefore pear- shaped with vanes attached to the cone of the tail to ensure that the bomb drops nose first. method of detonation.—to detonate the it.e. filling on impact with the target, fuses or pistols are used. these are usually sim- ple mechanisms depending for their arming on the unscrewing of vanes by the air stream whilst falling. the germans gave a rotary flight to some of their bombs by twisting the vanes so that a safety device, worked by centrifugal action, could be in- corporated, but this tends to slow down the flight of the bomb. in general a safety pin, which is only withdrawn from the fuse when the airman drops the bomb, is used as an additional safety precaution. the building up of the detonation wave is accom- plished by a central exploder which may run the whole length of the bomb or, as in gun shell, only a few inches into the h.e. filling. magazines and shell stores a magazine is a building with passages leading thercto, in which are stored explosives in bulk which must be under special magazine conditions with regard to precautions against fire or explosion. an explosive store is a building, standing apart from others, used for storage of explosives which are not necessarily kept under magazine conditions. a shell store is a store in which filled shell are kept. although in england the explosives act, 1875, expressly ex- amplifier empts government magazines from its provisions, the conci- tions imposed by the act apply generally to them. afaguszite regitlations, 1922, lays down in detail the principles governing the arrangement for a magazine in great britain as regards site, construction and working conditions. for explosive stores the regulations for magazines are modified as regards the neces- sity for special clothing and certain minor conditions, but otherwise magazine regulations should generally be strictly enforced. for the purpose of storage and transport all service explosives are classified in mfagasine regulations, 1922, into groups, and the regulations specify the class of store in which each group is kept. the principles on which this classification is made are based on the stability of the explosive, its liability to decomposi- tion, the ease with which it ignites or explodes and similar properties. for example, explosives hable to decomposition and bearing an explosion risk must be kept in a magazine. in for- tresses and defensive works magazines and stores require special protection from enemy fire, which is ordinarily provided by heavy traverses. magazine safety regulations are rigidly en- forced, but certain variations in storage are permitted under special conditions. arrangements for war—in a theatre of war arrangements must be improvised to conform as far as possible to magazine regulations as regards the provision of buildings or shelters, but safety regulations should be invariably observed. wooden huts, with corrugated iron roofs, can be employed in connection with storage of explosives and ammunition; a height of 8 to ro ft. from floor to eaves would be suitable, and such huts can be made splinter-proof by layers of sandbags. a large storage hut may occupy 4 space 30 ft. wide by 300 ft. long, and would be divided into compartments or bays by traverses made of double walls of galvanised iron sheeting. a floor of road metal, rammed hard, would suffice. when a building is not available, a raised floor with tarpaulin supported on a framework so as to allew of ven- tilation, is readily improvised. all explosives should be kept in substantial cases or receptacles where possible. all ammuni- tion necessarily kept in the open should be stored on battens and covered with tarpaulins, which covering should be removed whenever conditions are favourable, in order to permit of ventilation and to prevent sweating. when shells are piled in the open they should never be exposed to the direct rays of the sun. at base depets and advanced depets arrangements for storage of ammunition can be made on more or less semi-permanent lines. from these depets, the ammunition passes to ammuni- tion parks and columns where the arrangements have to be improvised as local conditions permit. with mobile warfare the movements of parks and columns would prevent any arrange- ments for storage, separate from the vehicles, of more than a temporary character, as the principal object would be to deliver, as rapidly as possible, ammunition from the depets to the par- ticular batteries where it might be most urgently required. yor trench warfare, the system of dumps was employed to facilitate ready supply of large quantities of munitions. these dumps would be classified according to the nature of the ammuni- tion and might be mere stacks in the open, separated by trav- erses of sandbags. convenience of transport and local condi- tions would be the main factors in determining the position and extent of these dumps. (c. w. f.) amplifier: see broadcasting; micropiione; telegrapil; telephone; wireless telfegraphy.—amplifiers are used generally either in connection with systems of electrical communication or for rendering sounds and othcr vibrational waves perceptible that would otherwise be too faint to be heard. the essential features of an amplifier are a source of energy, such as a battery, and means whereby the flow of energy from this source may be so controlled by the wave to be amplified that the variations of the original wave are repro- duced upon an enlarged scale in the wave set up by this flow. practically all of the amplificrs in use up to rgto depended upon variations in the electrical resistance of a mass of granular “ amritsar—anaemia carbon which result from variations in mechanical pressure, as in the telephone transmitter. here the power associated with the electric wave may be as much as 1,000 times that of the sound wave. for amplilying weak alternating electric currents of voice frequency, a combination of telephone receiver and transmitter having a common diaphragm was used. ‘this so-called “ me- chanical repeater ” was used on telephone lines. various other devices based on changes in resistance with mechanical motion were developed to meet particular needs, notably those of sub- marine cable telegraphy. types in use.—with the beginning of the period 1910-26, the amplifying possibilities of electric discharge devices were coming to be recognised. amplifiers of this kind fall into two classes— the so-called negative resistance devices, which have only two terminals; and those having separate input and output terminals corresponding to those of the mechanical repeater. the former include discharge devices such as arcs, in which the voltage be- tween the electrodes decreases with increasing current. owing to their extreme instability, very little practical application has been found for them. of the second class by far the most important is the three- electrode thermionic discharge type variously known as audion, valve, triode, vacuum tube and pliotron. in this type the path of the current from the battery includes a discharge between two electrodes in an evacuated vessel. the discharge is made possible by the emission of electrons from a hot cathode, usually a fila- ment through which an auxiliary heating current is passed. the anode may be either a plate or a cylinder concentric with the filament. the flow of current is controlled by the potential of a third electrode, or grid, situated between the anode and the cath- ode. the discharge passes through openings in this electrode. ‘the source of the wave to be amplified is connected, usually through a voltage step-up transformer, with the grid and the filament, so that the potential of the grid relative to the fllament varies in accordance with the wave to be amplified. the output circuit, which includes the path between the plate and the fila- ment together with a load circuit, has set up in it an amplified copy of the impressed wave. the carbon amplifier, besides its use as a telephone transmit- ter, has been applied to submarine and subterranean signalling and to the detection or location of airplanes, submarines, mining operations and gunfire. thermionic amplifiers are widely used in wire telephone and loud-speaker systems, in submarine cable telegraphy, and in high-frequency telephony and _ telegraphy by wire and by radio for amplifying both high- and low-frequency currents. they make possible more refined electric and other measurements, and have a varicty of miscellaneous applications in special fields such as in aiding the deaf to hear and in making heart sounds more readily audible. (r. v. l. hh.) brnirography.—e. h. armstrong, “‘ some recent developments in the audion receiver,’”’ proc. inst. radio eng., vol. 3 (1915); langmuir, ‘‘ the pure electron discharge and its applications in radio telegraphy and telephony,” ziid. (1915); h. barkhausen, “die vakuumrohre und ihre technischen anwendungen,” jahrb. | draht. teleg. u. teleph., vol. 14 (1919); vol. 16 (1920); vol. 18 (1921); j. r. carson, “ a theoretical study of the three-element vacuum tube,”’ proc. inst, radio. eng., vol. 7 (1919); b. gherardi and f. b. jewett, “telephone repeaters,’’ trans. amer. inst. flec. eng., vol. 38 (1919); h. w. nichols, ‘‘ the audion as a circuit element,” physical rev., vol, 13, ser. 2 (1919); l. deforest, ‘‘ the audion —its action and some recent applications,”’ franklin inst. jour., vol. 190 (1920); h. j. van der biji, the thermionic vacnum tube and its applications (1920); r. w. king, “ thermionic vacuum tubes and their applications,” bell. system technical jour., vol. 2 (oct. 1923); j. a. fleming, the thermionic valve and its developmenis in radio- telegraphy and telephony, 2nd ed. (1924). amritsar (see 1.895), the wealthiest town after delhi in the punjab, had in 1921 a population of 160,218, mostly moslem and hindu. there are about 200 looms engaged in the carpet- making industry, and the town has some commercial impor- tance, as apart from the entrepdet trade in piece goods, a large business in skins and hides is carried on. the two yearly fairs are the most widely attended in the province. the foundation stone of a new hospital was laid in 1917. 119 as a result of the intense feeling aroused by the rowlatt act, banks and other buildings were pillaged and burnt and europeans murdcred in the town in 1919, and the civil authori- ties called for military assistance. on april 13 the so-called tragedy of amritsar occurred, when gen. dyer found it neces- sary to disperse an unlawful gathering in the jallianwala dagh, and as a result nearly 400 natives were killed by gunfire, and probably three times that number wounded. this, and the administration of martial law proclaimed the following day aroused bitter indignation, which was not allayed by the appointment later of the hunter committee to enquire into the disturbance. owing to this incident many moderate indian politicians were alienated from british rule, but among the british community in india and elsewhere general dyer found many sympathisers in the difficulty in which he had been placed. see india. amsterdam (see 1.8096) had in 1923 a population of 706,194. the city suffered considerably during the world war from the loss of a great part of the former extensive financial busi- ness. the stock exchange was closed in aug. 1914, but reopened on feb. 9 1915. there followed a stagnant period, with little international business. immediately after the war a very difficult period set in; but the sound tactics pursued by am- sterdam bankers resulted in the florin reaching par before the end of 1924; shipping on the rhine increased after the german mark had been stabilised and conditions in the ruhr had improved. the total goods traffic of the port increased 50% between 1913 and 1924. the coen harbour, on the south side of the y, with 3,112 ft. of quays for seagoing ships and 2,000 ft. for river craft, was opened in 1924, and plans were prepared for a new lock 1,292 ft. long at the entrance to the north sea canal at ¥muiden. the canal itself was dredged to a depth of 33 ft., and a new canal to improve the connection between amsterdam and the rhine was recommended, which would accommodate the largest barges in use on the rhine, connect with the existing canal at utrecht and be carried across the dutch rhine to tiel. the railway line between amsterdam and the hague was being electrified in 1926. _ amundsen, roald (1872- ), norwegian explorer, was born july 16 1872, in borge, a country district near sarpsborg in southeastern norway. educated at christiania (now oslo) he took his b.a. degree in 1890 and began to study medi- cine, but gave it up and went to sea in 1894. during the follow- ing nine years, amundsen, with the tenacity of purpose which was one of his chief characteristics, prepared himself for his future career as an explorer, and in 1903-6 he led an expedition consisting of himself and six companions through the north west passage, on board the “ gjia,” a little sloop of 47 tons. simultaneously he succeeded in fixing the position of the mag- netic north pole. his next expedition, on board the ‘ fram,” originally intended as a north polar expedition, by a dramatic surprise, became a south polar expedition (1910-2), and was the first actually to reach the south pole. after his return in 1913 he resumed his preparations for a north polar expedition but was stopped by the outbreak of the world war. he remained inactive until 1918 when he left norway on board the ‘‘ maud,” a new vessel, with the aim of drifting from the north siberian is. across the polar basin. baffled in this undertaking owing to the fact that the polar stream did not prove to be constant, he decided to force the polar basin in an acroplane. on his fourth attempt he succeeded, using the semi-rigid dirigible “norge,” built in italy. starting with the american el!sworth, from spitsbergen, may 11 1926, he flew to the pole, which he circled twice, thence across the unexplored arctic basin to point bar- row, alaska, and finally landed may 14 at teller on behring sea. the total distance traversed was 2,700 m., the time occu- pied in the flight being only 71 hours. see polar exploration. anaemia.—a generic term for various forms’ of disease char- acterised by a defective constitution of the blood, or more specifically, by a reduction in the oxygen-carrying power of the blood. this reduction is due, either to a decrease in the num- ber of red blood corpuscles, or to a decrease in the amount of t20 haemoglobin they contain, haemoglobin being that constituent of the red corpuscles which makes it possible for them to carry oxy- gen to the tissues and to play an important rdele in the transfer of carbon dioxide from the tissues to the lungs. the amount of haemoglobin that each red corpuscle contains is represented by a term known as the cclour index, which is derived by dividing the percentage of haemoglobin by the percentage of red corpuscles. types of anaemia.—the existence of several kinds of anaemia is recognised. a satisfactory classification is impossible because of the incompleteness of our knowledge. the customary division is as follows: (a) the primary, those in which the cause is yet unknown; and (6) the secondary, those due to some known cause. chlorosis and pernicious anaemia are primary anaemias. the anaemia caused by haemorrhage, malaria, chronic poison- ing by known chemical and biological agents, parasites, mal- nutrition, malignant disease, etc., is secondary. as our know- ledge increases, all the different anaemias in the course of time will probably become secondary. syntploms.—since the chief derangement in all anaemias is a reduction of the total amount of haemoglobin in the blood, the symptoms and pathological anatomy are quite similar in the different kinds of anaemia. [pallor of the skin and mucous mem- branes, shortness of the breath, palpitation, faintness, weakness, languor, headache, and usually gastro-intestinal disturbances, are the general symptoms. a special tendency to haemorrhage is frequently present. the physician frequently finds the heart to be dilated and hears systolic murmurs in the heart on aus- cultation. anatomically the internal organs are pale, sometimes smaller than normal and atrophic, and their cells contain an excessive amount of fat. the spleen is enlarged in some anaemias and is usually of denser consistency than normal. vhe red bone- marrow, which forms the red corpuscles and haemoglobin, is in- creased in amount except in rare cases. the diagnosis depends on the clinical picture, the examination of the blood, and a number of other findings. causative factors —obviously anaemia must be due to either one or a combination of the following factors: loss of blood, increased destruction of red corpuscles, or a disturbance of the red bone-marrow (erythroblastic tissue), leading to a decrease in the normal supply of red corpuscles or to a decrease in the amount of haemoglobin they contain. ‘the red bone-marrow in health continually supplies the blood with red corpuscles which contain a constant amount of haemoglobin to take the place of those destroyed in the liver, spleen and other tissues; so that the number of red corpuscles and the total amount of haemo- globin in the blood remain quite constant. if blood is lost, or if there is an increase in the destruction of red corpuscles, the red bone-marrow compensates by producing red corpuscles at a more rapid rate than normal. in such a case, especially if the loss, or destruction, is great, the red corpuscles so produced are frequently small, contain a subnormal amount of haemoglobin and may even contain a nucleus, which denotes that the cell is young. in the course of time these abnormal cells are replaced by normal cells and the red bone-marrow returns toa normal rate of production. but if the loss or destruc- tion is continuous or intermittent, as in chronic anaemias, the blood contains more and more abnormal red corpuscles. the erythroblastic tissue further attempts to compensate for this continuous demand for red cells by invading and replacing the yellow marrow which does not form red corpuscles. if the de- mand is in excess of the capacity of the erythroblastic tissue to respond, the condition of the blood seen in the chronic anaemias develops, namely, a decrease in the number of red corpuscles, the presence of abnormal types of corpuscles, and a diminution of the total amount of haemoglobin in the blood. in some of the anacmias it is possible to state definitely which of the above factors are concerned; in others opinion can be based only upon an interpretation of the known facts. in the anaemia that follows repeated haemorrhage, as occurs in ulcers of the gastro-intestinal tract, the obvious factor is the loss of blood. in the anaemias caused by haemolytic toxins, the de- anaemia struction of red corpuscles is the chief factor concerned, although these toxins may also act on the erythroblasts or embry- onic red corpuscles in the bone-marrow. in the anaemia secondary to malignant disease, e.g., gastric cancer, the anaemia is due to a combination of several factors: the loss of blood from haemorrhage; an increase in the destruction of red cor- puscles in some cases; a disturbance of nutrition leading to a lack of proper food supply for the erythroblastic tissue; and the pos- sible action of the autolytic products of the cancer cells which may inhibit the activity of the bone-marrow. the evidence of increased red corpuscle destruction can sometimes be obtained by examination of the spleen and liver, their cells containing a larger quantity of iron than normal, by examination of secre- tions or excretions, such as the bile and urine (haemoglobinuria), and by determining the fragility of the red corpuscles. ‘the fragility of the red corpuscles is ascertained by determining their ability to withstand a hypotonic solution of sodium chloride without disintegrating, normal red corpuscles being able to re- sist ao-4% solution, whereas “ fragile corpuscles ”’ will discharge their haemoglobin in a 0-5% solution. the evidence of dis- turbance of the red bone-marrow is obtained by detailed exam- ination of the blood, the cellular constituents being markedly altered. in the chronic anaemias regencration and destruction, or loss, occur simultaneously, so that the blood picture gives an idea more of the capacity of the erythroblastic tissue to re- spond than of the amount of destruction that is occurring. in aplastic anaemia, a rare condition, the red bone-marrow does not respond, and as a result the anaemia runs a rapid and progressive course without remissions, contrary to the usual course of the chronic anaemias. chloresis —chlorosis and pernicious anaemia are primary anaemias that deserve special discussion because of their common occurrence. chlorosis occurs almost exclusively in females between the ages of 14 and 25s, the most frequent ages of onset being 14 and 15. this disease is characterised by a pronounced haemoglobin deficiency without a proportional decrease in red corpuscles. it is rarely directly fatal and is fortunately very amenable to treatment with iron preparations, blood transfu- sions being required only in advanced and stubborn cases. the administration by mouth of bone-marrow and spleen is also, beneficial. recurrences of the «dlisease are quite common. the cause of chlorosis is unknown. all evidence shows that a haemo- lytic agent is probably not responsible. the erythroblastic tissue is at fault, particularly in the formation of haemoglobin. the fact that iron is so beneficial suggests that iron starvation is in some way related to the primary cause, which is also related in some way to the age of puberty and the function of menstruation. because of this latter factor, some believe that the glands of internal secretion, especially the ovary, are at fault; but no conclusive evidence is as yet available. an improper diet, over- work, worry and lack of fresh air are predisposing factors. chlorosis does not occur frequently in country-bred girls, which is probably due to the greater exposure to sunshine and “ out- door life,’ which these girls enjoy. the symptoms of chlorosis are in general those of anaemia. pernicious anaemia.—vernicious anaemia is a common disease but is less frequent in occurrence than chlorosis. it is a disease of middle life and is twice as common in males as in females. it is characterised by a progressive anaemia interrupted by periods of temporary improvement, and by a fatal termination almost without exception in from two to five years, the body being rarely emaciated. the onset of this disease is slow and insidious. the skin is pale and later takes on a lemon tint. lan- guor, weakness and breathlessness are not marked at first, but later become extreme. ‘the heart palpitates readily. the mucous membrane of the mouth is glossy and appears blood- less; the tongue is sore. the appetite fails and quite early in the disease acid disappears from the gastric secretion. attacks of diarrhoea and abdominal pain frequently occur. there is a tendency to bleed into the skin and serous surfaces. some pa- tients experience sensations of numbness and tingling and com- plain of neuritic pains. anaesthetics the blood picture is very abnormal, the ‘red corpuscles being markedly reduced in number and very abnormal in shape and size, as well as in other respects. the red corpuscles contain an abundance of haemoglobin, the colour index being greater than t-o. the white blood corpuscles are generally normal or dimin- ished in number, but frequently abnormal forms are present. on post-mortem examination the bone-marrow is red and hyper- plastic, except in cases of aplastic anaemia; lesions of the spinal cord are found; the gastric mucosa is frequently atrophic; the internal organs show fatty degeneration; the lymph glands may be deepened in colour (haemo-lymph glands), and there is much iron pigment in the kidneys, liver and spleen. in contrast to chlorosis, there appears to be no serious difliculty in the formation of haemoglobin in pernicious anaemia. many evidences of excessive blood destruction are present, particularly the increased iron content of the organs, free haemoglobin in the blood serum and urine, the frequent occurrence of jaundice, and the increased fragility of the red corpuscles. a condition simulating pernicious anaemia occurs on continued poisoning with toluylendiamine and ricin and in patients infected with bothriocephalus, an intestinal parasite that produces an haemo- lytic agent. haemolytic substances are said to be present in the intestine of anaemic patients that have chronic intestinal disorders, and recently a condition similar to pernicious anaemia has been ob- served to occur following intestinal stasis. b. aerogenes capsula- tus, which frequently inhabits the intestine of man, produces an haemolytic agent, and it is reported that they occur in increased numbers in the intestine of patients that have pernicious anae- mia and that their number decreases during the remissions. the feeding of this bacterium 1n large numbers, or the intra- venous injection of their products, produces in animals a con- dition quite like pernicious anaemia in man. buckman and horrall report that an haemolytic substance is present in the serum of pernicious anaemia patients. some observers believe that the stomach is in some way related to the cause because of the high incidence of absence of acid in the stomach (achlorhydria) of patients suffering with this disease and because this disease sometimes occurs after total removal of the stomach. the absence of the acid in the stomach is said to favour the growth of bacteria that produce haemolytic poisons. after total gastrectomy in dogs a grave anaemia is found, which, however, has been controlled by the administra- tion of tron and cad-liver oil. tt is impossible to state at this time whether the change in the stomach is primary or secondary. although the more recent evidence seems to show that it is primary, it is commonly held to be secondary, as are the changes in the bone-marrow and nervous system, to the action of a toxin, irrespective of its source. all treatments at present can be said to be only palliative. the source of the toxaemia should be looked for. nutritious and readily digestible foods should be ingested, and plenty of fresh air, sunlight and cod-liver oil are indicated. dilute hydro- chloric acid by mouth improves digestion. removal of the spleen has been tried extensively, but without definite benefit. it is of great bencfit, however, in splenic anaemia. repeated blood transfusion quite probably offers more for pernicious anaemia than any other form of treatment. other forms of anaemta.—there are other diseases of the blood and blood-forming organs, such as lymphosarcoma, hodgkin’s disease, chloroma, leucaemia and anaemia pseudo- leucaemia of children, in which anaemia occurs. in these dis- eases the disturbance chiefly involves the white corpuscles, or leucocytes, and hence these diseases are not to be considered in a general discussion of anaemia. bipiiograruy.—f. b. mallory and j. h. wright, pathological technique (1918); anders, am. jour. med. sci., vol. 158, p. 659 (1919); f. vice, practice of medicine, vol. 6 (1921); a. f. hurst, guy's hosp. rep., vol. 73 (1923) and lancet (jan. and june 1923); faber and gram, arch. int. afed., vol. 34, p. 827 (1924); ivy and farrell, proc. am. physiol. soc. (dec. 1925); kahn and torrey, jour. inf. dis., vol. 37, p. t6t (1925). (ar csi) i21 anaesthetics (sce 1.907).—the agents for producing general surgical anaesthesia which were the first to be introduced, that is, nitrous oxide gas, ether and chloroform, not only remain in general use, but actually provide in greater part for the require- ments of modern surgery. local anaesthesia, which has in part supplanted general anacsthesia, has still only a very limited application. nitrous oxide.—the war showed that persons suffering from severe shock and loss of blood from wounds did not progress favourably following operations under chloroform or ether, but that the prospects of recovery were distinctly improved when performed under the continuous inhalation of nitrous oxide gas. the reasons for this cannot be stated precisely, but it may be said in general terms that nitrous oxide is less depressing, and further that owing to its exceedingly rapid excretion, conscious- ness and normal bodily conditions are quickly restored after com- pletion of the operation. nitrous oxide or “ laughing gas,” as it was formerly termed, is familiar as an agent for producing brief periods of narcosis, as for the extraction of teeth. when administered thus in a pure state it excludes the admission of air to the lungs and if continued would cause complete asphyxia. the problem of continuous administration is therefore the admission of sufficient oxygen to the lungs to satisfy the needs of the body. air contains about one-fifth of its volume of oxygen, but if nitrous oxide were di- luted to this extent its partial pressure would be reduced to about 80%, which is too weak for the convenient production of its full anaesthetic effect, at least in the early stages of its administration. oxygen may in fact be reduced to a proportion of one-tenth of an atmosphere without causing discomfort to the patient or even under ordinary circumstances causing the dis- colouration of the face known as cyanosis. it may even be re- duced lower than one-tenth and yet be capable of sustaining life. the continuous administration of nitrous oxide mixed with oxygen requires a sufficiently delicate mechanism to regulate and indicate the relative proportions of the gases, but it isnot a method which is adapted for all classes of cases; the relaxation of the body muscles is not sufficient for the convenient performance of certain operations; the narcosis is not always sufficiently deep and it may have to be supplemented by an admixture of ether vapour; nor is it absolutely free from danger. its advantages in the cases of profound shock referred to appear to be undoubted, but it can not be classed for precision of action with the routine anaesthetics, chloroform and cther. dither.—the use of ether as an anaesthetic has received con- siderable stimulus from the introduction of the “‘ open ” method of administration. in order to induce anaesthesia in a muscular person, or “ to get him under ” in ordinary phraseology, a strong vapour may be required, this bcing as strong as 25° to 30% in some cases. in the “ open ” ether method the breathing is noiseless, effort- less, and only slightly exaggerated, so that delicate abdominal operations can be performed with comfort. the flow of saliva is considerably less than in the closed method, probably from the absence of asphyxia, and this can be entirely abolished by the subcutaneous injection of a minute dose of atropine previous to the administration. there is no sign of cyanosis, and the patient’s face remains a healthy colour throughout; the only re- striction of oxygen is by reason of the displacement of air by ether vapour which at a maximum will be less than one-third its volume, and as in the later stages of an administration much jess vapour is required, the restriction becomes entirely negli- gible. the after-effects of ether, such as vomiting and malaise, are considerably less pronounced than those that follow a “close ’? administration. the application of the “ open” method to ether inhalation has been brought about by an exceedingly simple adaptation. the liquid ether is applied to a pad of open-wove fabric, such as “ stockinette ’ or a number of layers of absorbent gauze stretched over a framework mask of which the margin is roughly adapted to the contours of the face; the mask rests lightly upon the face, a soft pad being interposed between its edges and the 122 skin to prevent the entrance of air in this direction. in this way the inhaled air passes through the meshes of the fabric and in doing so every portion of it comes in close contact with the ether and takes up a greater proportion of vapour than it would if it merely passed over the surface of the fabric. the induction of anaesthesia by the “ open ” method is liable to be somewhat prolonged, an undoubted disadvantage, but once full anaesthesia has been produced it is maintained without difh- culty and the results attained are in general more satisfactory than those of any other form of inhalation anaesthesia. the “ intratracheal’ method of etherisation is conducted by passing a narrow tube through the larynx into the trachea almost to the level of its bifurcation. through this tube a contin- uous current of air and ether vapour is forced into the lungs at a pressure which keeps the lungs moderately distended, but not so much as to abolish the natural respiratory movements. the air returns through the chink of the vocal cords by the side of the tube and this continuous return blast blows away any solid or fluid particles, blood or pieces of tissue, in the neighbourhood, and prevents their entering the trachea, an accident which may possibly occur in ordinary inhalation methods. ‘the advantage of intratracheal ether in operations involving the respiratory pas- sages is therefore obvious; it is likewise a convenient arrangement for operations upon the face, which is left entirely uncovered, and in operations upon the interior of the thorax a proper aeration of the lungs can be thus ensured. chloreform.—the form of sudden death which is occasionally encountered under chloroform anaesthesia has acted as a deter- rent to its more extended employment in spite of its manifest conveniences, it is now becoming realised that the typical sudden chloro- form fatality is not conditioned by an overdose as formerly supposed. it has long been known that the majority of deaths occur in the very early stages of anaesthesia before the patient is fully narcotised, and further examination of reports of fa- talities shows that there is generally some evidence of light anaesthesia preceding death, or else that overdosage can be ruled out of question. there is a further point brought out by these reports, which was in fact fully appreciated by john snow in the middle of the jast century: whereas in overdose the res- piration is paralysed before the circulation, in the typical chloro- form death the outstanding feature is an absolutely sudden failure of the circulation, and the failure of the respiration is a secondary result. dr. a. g. levy, in 1911, reported certain cases of sudden cardiac failure that he had observed in animals obviously in a light stage of chloroform anaesthesia, and he succeeded in re- producing this death by the intravenous injection of small doses of adrenalin in lightly chloroformed animals, but the experiment failed under full chjoroform narcosis. this at once accounted for those cases of syncope and death, a number of which had been recorded, following the injection of adrenalin into the mucous membrane of the nose for the purposes of certain nasal opera- tions which were always conducted under light anaesthesia, the form of this syncope being the same as in an ordinary chloroform fatality. by following up this line of research it was shown that sudden cardiac failure could be induced likewise by various procedures— excitation of the cardiac accelerator nerves either directly or through a reflex mechanism, stimulating the excretion of the adrenal glands, by intermitting the administration of chloro- form, or by withholding the chloroform during excitement and struggling; the event never occurred during deep narcosis. the underlying condition of the cardiac syncope was shown to be that of fibrillation of the ventricles, in which the ventricles are entirely deprived of their power of propelling the blood through the arteries. on this theory death under chloroform can be prevented by simple precautions, by muking the induction of anaesthesia continuous and expeditious and thereafter continuously main- taining a full degree of narcosis. chloroform should never be employed if the conditions of the operation forbid the observ- anatolia—anatomy ance of these rules and especially in those special cases in which a light degree of anaesthesia is required. (see etnyi ciloripe; ethylene.) brpciography.—j. f. w. silk, afedern anaesthetics (1920); j. blomfield, anaesthetics in practice and theory (1922); sir w. hewitt, avaesthetics and their administration (1922); a. g. levy, chloroform anaesthesia (1922). cn cg at anatolia: see asia minor; turkfy.",
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