LYMINGTON

lymington, a municipal borough and seaport in the new forest parliamentary division of hampshire, england, 98 m. s.w. from london by the london & south western railway. pop. (1901) 4165. it lies on the estuary of the lymington, which opens into the solent. the church of st thomas a becket is an irregular structure, dating from the reign of henry vi., but frequently restored. there is some coasting trade, and yacht-building is carried on. regular passenger steamers serve yarmouth in the isle of wight. in summer the town is frequented for sea-bathing. it is governed by a mayor, 4 aldermen and 12 councillors. area, 1515 acres. there was a roman camp near lymington (_lentune_, _lementon_), and roman relics have been found, but there is no evidence that a town existed here until after the conquest. lymington dates its importance from the grant of the town to richard de redvers, earl of devon, in the reign of henry i. no charter has been found, but a judgment given under a writ of _quo warranto_ in 1578 confirms to the burgesses freedom from toll, passage and pontage, the tolls and stallage of the quay and the right to hold two fairs--privileges which they claimed under charters of baldwin de redvers and isabel de fortibus, countess of albemarle, in the 13th century, and edward courtenay, earl of devon, in 1405. the town was governed by the mayor and burgesses until the corporation was reformed in 1835. a writ for the election of a member to parliament was issued in the reign of edward iii., but no return was made. from 1585 two members were regularly returned; the number was reduced to one in 1867, and in 1885 the representation was merged in that of the county. fairs on the 13th and 14th of may and the 2nd and 3rd of october, dating from the 13th century, are still held. the saturday market probably dates from the same century. lymington was made a port in the reign of henry i., and its large shipping trade led to frequent disputes with southampton as to the levying of duties. the case was tried in 1329 and decided against lymington, but in 1750 the judgment was reversed, and since then the petty customs have been regularly paid. from an early date and for many centuries salt was the staple manufacture of lymington. the rise of the mineral saltworks of cheshire led to its decline in the 18th century, and later the renewed importance of southampton completed its decay. see e. king, _borough and parish of lymington_ (london, 1879). lymph and lymph formation. lying close to the blood-vessels of a limb or organ a further set of vessels may be observed. they are very pale in colour, often almost transparent and very thin-walled. hence they are frequently difficult to find and dissect. these are the lymphatic vessels, and they are found to be returning a fluid from the tissues to the bloodstream. when traced back to the tissues they are seen to divide and ultimately to form minute anastomosing tubules, the _lymph capillaries_. the capillaries finally terminate in the spaces between the structures of the tissue, but whether their free ends are closed or are in open communication with the tissue spaces is still undecided. the study of their development shows that they grow into the tissue as a closed system of minute tubes, which indicates that in all probability they remain permanently closed. if we trace the lymphatic vessels towards the thorax we find that in some part of their course they terminate in structures known as lymphatic glands. from these again fresh lymphatic vessels arise which carry the fluid towards the main lymph-vessel, the _thoracic duct_. this runs up the posterior wall of the thorax close to the aorta, and finally opens into the junction of the internal jugular and left subclavian veins. the lymph-vessels from the right side of the head and neck and from the right arm open, however, into the right subclavian vein (see lymphatic system below). _chemical constitution of lymph._--the lymph collected from the thoracic duct during hunger is almost water clear and yellowish in colour. its specific gravity varies from 1015 to 1025. it tastes salt and has a faint odour. it is alkaline in reaction, but is much less alkaline than blood-serum. like blood it clots, but clots badly, only forming a soft clot which quickly contracts. the lymph collected from a lymphatic before it has passed through a lymph gland contains a few leucocytes, and though the number of lymphocytes is greater in the lymph after it has flowed through a gland it is never very great. in normal states there are no red blood corpuscles. the total solids amount to 3.6 to 5.7%, the variations depending upon the amount of protein present. the lymph during hunger contains only a minute quantity of fat. sugar (dextrose) is present in the same concentration as in the blood. the inorganic constituents are the same as in blood, but apparently the amounts of ca, mg and p2o5 are rather less than in serum. urea is present to the same amount as in blood. if the lymph be collected after a meal, one important alteration is to be found. it now contains an abundance of fat in a very fine state of subdivision, if fat be present in the food. the concentrations of protein and dextrose are not altered during the absorption of these substances. _the significance of lymph._--in considering the significance and use of lymph we must note in the first place that it forms an alternative medium for the removal of water, dissolved materials, formed elements or particles away from the tissues. all materials supplied to a tissue are brought to it by the blood, and are discharged from the blood through the capillary wall. they thus come to lie in the tissue spaces between the cells, and from this supply of material in a dissolved state the cells take up the food they require. in the opposite direction the cell discharges its waste products into this same tissue fluid. the removal of material from the tissue fluid may be effected either by its being absorbed through the capillary wall into the bloodstream, or by sending it into the lymphatic vessels and thus away from the tissue. from this point of view the lymphatics may be looked upon in a sense as a drainage system of the tissues. again, besides discharging fluid and dissolved material into the tissue spaces, the blood may also discharge leucocytes, and under many conditions this emigration of leucocytes may be very extensive. these also may leave the tissue space by the path of the lymph channels. moreover, the tissues are at any time liable to be injured, and the injury as well as damaging many cells may cause rupture of capillaries (as in bruising) with escape of red blood-cells into the tissue spaces. if this occurs we know that the damaged cells are destroyed and their debris removed either by digestion by leucocytes or by disintegration and solution. the damage of a tissue also commonly involves an infection of the damaged area with living micro-organisms, and these are at once admitted to the tissue spaces. hence we see that the lymphatics may be provided as channels by which a variety of substances can be removed from the tissue spaces. the question at once arises, is the lymph channel at all times open to receive the materials present in the tissue space? if such be the case, lymph is simply tissue fluid, and anything that modifies the constitution or amount of the tissue fluid should in like proportion lead to a variation in the amount and constitution of the lymph. but if the lymph capillary is a closed tubule at its commencement this does not follow. from these considerations we see that in the first instance the whole problem of lymph formation is intimately bound up with the study of the interchanges of material between the blood and the various tissue cells. the exchange of material between blood and tissue cell may possibly be determined in one or both of two ways. either it may result from changes taking place within the tissue cell, or the tissue cell remaining passive material may be sent to or withdrawn from it owing to a change occurring either in the composition of the blood or to a change in the circulation through the tissue. let us take first the results following increased activity of a tissue. we know that increased activity of a tissue means increased chemical change within the tissue and the production of new chemical bodies of small molecular size (e.g. water, carbonic acid, &c.). the production of these metabolites means the destruction of some of the tissue substance, and to make good this loss the tissue must take a further amount of material from the blood. we know that this takes place, and moreover that the waste products resulting from activity are ultimately removed. the question then becomes: when does this restoration take place, and what is the intermediate state of the tissue? we know that increased activity is always accompanied by an increase in the blood-supply, indicating a greater supply of nutritive material, though it may be that, the increased supply required at the actual time of activity is oxygen only. simultaneously the opportunity for a more rapid removal of the waste products is provided. we have to inquire then: does this increased vascularity necessarily mean an increased outpouring of water and dissolved material into the tissues, for this might follow directly from the greater filling of the capillaries, or from the increased attracting power of the tissues to water (osmotic effect) due to the sudden production of substances of small molecular size within the tissue? the other possibility is that the increased volume of blood sent to the tissue is for the sole purpose of giving it a more rapid supply of oxygen, and that the ordinary normal blood-supply would amply suffice for renewing the chemical material used up during activity. tissues undoubtedly vary among themselves in the amount of water and other materials they take from the blood when thrown into activity, and their behaviour in this respect depends upon the work they are called upon to perform. we must discriminate between the substance required by and consumed by the tissue, the chemical food which on combustion yields the energy by which the tissue performs work, and, on the other hand, the substance taken from the blood and either with or without further elaboration discharged from the tissue (as, for instance, in the process of secretion). the tissue contains in itself a store of food amply sufficient to enable it to continue working for a long time after its blood-supply has been stopped, and everything indicates that the supply of chemical energy to the tissue may be slow or even withheld for a considerable time. hence we are led to conclude that the increased flow of blood sent to a tissue when it is thrown into activity is first and foremost to give that tissue an increased oxygen supply; secondly, to remove waste carbonic acid; thirdly, and only in the case of some tissues, to provide water salts and other materials for the outpouring of a secretion, as an instance of which we may take the kidney as a type. hence there is no need to suppose that an extensive accumulation of fluid and dissolved substances takes place within a tissue when it becomes active. this must be an accumulation which would lead to an engorgement of the tissue spaces and then to a discharge of fluid along the lymph channels. to enable us to determine the various points just raised we must know whether an increased blood-supply to a tissue necessarily means an increased exudation of fluid into the tissue spaces, and moreover we must study the exchange of fluid between a tissue and the blood under as varied a series of conditions as possible, subsequently examining whether exchange of fluid and other substances between the tissue and the blood necessarily determines quantitatively the amount of lymph flowing from the tissue. hence we will first study the exchanges between the blood and a tissue, and then turn our attention to the lymph-flow from the tissues. _the exchanges of fluids and dissolved substances between the blood and the tissues._--numerous experiments have been performed in studying the conditions under which fluid passes into the tissues and tissue spaces--or in the reverse direction into the blood. we may group them into (1) conditions during which the total volume of circulating fluid is increased or decreased; (2) conditions in which the character of the blood is altered, e.g. it is made more watery or its saline concentration is altered; (3) conditions in which the blood-supply to the part is altered; (4) conditions in which the physical character of the capillary wall is altered. 1. the total volume of blood in an animal has been increased among other ways by the transfusion of the blood of one animal directly into the veins of a second of the same species. it is found that within a very short time a large percentage of the plasma has been discharged from the blood-vessels. it has been sent into the tissues, notably the muscles, and it may be noted in passing without producing any increase in the lymph-flow from these vessels. an analogous experiment, but one which avoids the fallacy introduced by injecting a second animal's blood, has been performed by driving all the blood out of one hind limb by applying a rubber bandage tightly round it from the foot upwards. this increases the volume of blood circulating in the rest of the body, and again a rapid disappearance of the fluid part of the blood from the vessels was observed--the fluid being mainly sent into the muscles, as was indicated by showing that the specific gravity of the muscles fell during the experiment. the experiments converse to these have also been studied. bleeding is very rapidly followed by a large inflow of fluid into the circulating blood--this fluid being derived from all the tissues, and especially again from the muscles. or again, when the bandage from the limb in the above-cited experiment was removed, the total capacity of the circulatory system was thereby suddenly increased, and it was found that the total volume of blood increased correspondingly, the increased volume of fluid being drawn from the tissues and especially again from the muscles. the rapidity with which this movement of fluid into or out of the blood takes place is very striking. the explanation usually offered is that the movement is effected by changes in the capillary pressure due to the alteration in the volume of blood circulating. while this seems feasible when the volume of blood is increased, it does not offer a satisfactory explanation of the rapid movement of fluid from the tissues when the volume of the blood is decreased. one must therefore look for yet further factors in this instance. 2. let us next turn attention to the second of our three main variations, viz. that in which the composition of the blood is altered. it has long been known that the injection of water, or of solutions of soluble bodies such as salts, urea, sugar, &c., leads to a very rapid exchange of water and salts between the blood and the tissues. thus if a solution less concentrated than the blood be injected, the blood is thereby diluted, but with very great rapidity water leaves the blood and is taken up by the tissues. again, if a strong sugar or salt solution be injected, the first effect is a big discharge of water from the tissues into the blood and the movement of fluid is effected with great rapidity. in these instances a new physical factor is brought into play, viz. that of osmosis. when a solution of lower osmotic pressure than the blood is injected the osmotic pressure of the blood falls temporarily below that of the tissues, and water is therefore attracted to the tissues. the converse is the case when a solution of osmotic pressure higher than the blood is injected. this at first sight seems to be an all-sufficient explanation of the results recorded, but difficulties arise when we find that the tissues are not equally active in producing the effects. thus it is found that the muscles and skin act as the chief water depot, while such tissues as the liver, intestines or pancreas take a relatively small share in the exchange. again, when a strong sodium chloride solution is injected a considerable part of the sodium chloride is soon found to have left the blood, and it has been shown that the chloride depot is not identical with the water depot. the lung, for instance, is found to take up relatively far more of the salt than other tissues. simultaneously with the passage of the salt into the tissue an exchange of water from the tissue into the blood can be observed, both processes being carried out very rapidly. the result is that the blood very quickly returns to a state in which its osmotic pressure is only slightly raised; the tissue, on the other hand, loses water and gains salt, and its osmotic pressure and specific gravity therefore rises. again, the tissues do not participate equally in producing the final result, nor is the tissue which gives up the largest amount of water necessarily that which gains the largest amount of salt. the results following the injection of solutions of other bodies of small molecular size, e.g. urea or sugar, are quite analogous to those above described in the case of the non-toxic salt solutions. hence we see that the rate of exchange of fluid and dissolved substance between a tissue and the blood can be extremely rapid and that the exchange can take place in either direction. we may also conclude that the main cause of the exchange, and possibly the only one, is the osmotic action set up by the solution injected, and that muscle tissue is particularly active in the process. seeing that a very considerable amount of water or of dissolved substance can be taken up from the blood into a tissue, the question next arises: where is this material held, in the tissue cell or in the tissue space? immediately the water or salt leaves the blood it reaches the tissue space, but unless the process be extreme in amount it probably passes at once into the tissue cell itself and is stored there. if the process is excessive oedema is set up and fluid accumulates in the tissue space. these, taken quite briefly, are some of the more important conditions under which fluid exchanges, take place. they are selected here because of the extent and rapidity of the changes effected. 3. the third factor which may bring about a change in the amount of fluid sent to a tissue is a variation in the capillary pressure. a rise in capillary pressure will, if filtration can occur through the capillary wall, cause an increased exudation of fluid from the blood. thus the rise in general blood-pressure following the injection of a salt solution could cause an increased filtration into the tissues. or again, the hydraemia following a salt injection would favour an increased exudation because the blood would be more readily filtrable. we, however, know very little of the effect of changes in capillary pressure upon movement of fluid into the tissue spaces and tissues, most of such observations being confined to a study of their effect upon lymph-flow. we will therefore return to them in this connexion. 4. the remaining factor to be mentioned is a change in the character of the capillary wall. it is well known that many poisons can excite an increased exudation from the blood and the tissue may become oedematous. of such bodies we may mention cantharidin and the lymphogogues of class i (see later). a like change is also probably the cause of the oedema of nephritis and of heart disease. it has also been suggested that the capillaries of different organs show varying degrees of permeability, a suggestion to which we will return later. _lymph formation._--there are two theories current at the present day offering explanations of the manner in which lymph is formed. the first, which owes its inception to ludwig, explains lymph formation upon physical grounds. thus according to this theory the lymphatics are open capillary vessels at their origin in the tissues along which the tissue fluid is driven. the tissue fluid is discharged from the blood by filtration, and therefore its amount varies directly with the capillary pressure. the amount of fluid movement also is further determined by osmotic actions and by the permeability of the capillary wall. the second theory first actively enunciated by heidenhain regards lymph formation as a secretory process of the capillary wall, i.e. one in the discharge of which these cells perform work and are not merely passive as in the former theory. as we shall see, it is now probable that neither theory is completely correct. in considering lymph formation we have to examine both the total amount of lymph formed in the body and the variations in amount leaving each separate organ under different conditions. in most investigations the lymph was collected from the thoracic duct, i.e. it was the lymph returned from all parts of the body with the exception of the right arm and right side of the head and neck. the collection of the lymph from organs is much more difficult to effect, and hence has not, to the present, been so extensively studied. we will consider first variations in the amount of the thoracic duct lymph. lymph is always flowing along the thoracic duct, and if the body is at rest, it has been shown that this lymph is coming practically entirely from the intestines and liver, chiefly, moreover, from the liver. the variations in the amount flowing under various conditions has been extensively studied. we will discuss them under the following headings: changes brought about (a) by altered circulatory conditions, (b) by the injection of various substances, and (c) as a result of throwing an organ into activity. ligature of the portal vein leads to an increased flow of duct lymph. ligature of the inferior vena cava above the diaphragm also leads to a large increase in the flow of duct lymph. ligature of the aorta may result in either an increased or decreased flow of direct lymph. one explanation of these results has been offered from a study of the changes in capillary pressure set up in the main organs involved. thus, after ligature of the portal vein the capillary pressure in the intestines rises, and it was proved that the increase in thoracic duct lymph came from the intestines. ligaturing the inferior vena cava causes a big rise in the pressure in the liver capillaries, the intestinal capillary pressure remaining practically unaltered. here it was proved that the increase in lymph-flow came from the liver and was more copious in amount than in the former instance. a further difference is that this lymph is more concentrated, a feature which always characterizes liver lymph. ligature of the aorta may or may not cause a rise in the liver capillary pressure, and it has been shown that if the pressure rises there is an increased lymph-flow from the liver and conversely. the increase of lymph comes entirely in this instance also from the liver. it is in fact but a special instance of the former experiment. from these results it has been argued that lymph formation is simply a filtration fundamentally, and the lymph-flow is determined mainly by the capillary pressure. variations in the quantity of lymph issuing from different organs have been on this theory ascribed to differences in the permeability of the capillaries of the organs. thus as liver lymph is richest in protein content and is produced in greatest amount, it has been concluded that the liver capillaries possess the highest permeability. the intestines stand next in producing a concentrated lymph, and their capillaries are therefore assumed to stand second as regards permeability. lastly, the lymph coming from limbs and other organs is much poorer in solids and much less copious in amount. hence it is argued that their capillaries show the least permeability. it is, however, very unsafe to compare the liver capillaries with those of other organs, since they are not in reality capillaries but rather venous sinuses, and their relation to the liver cells is characteristically different from that of ordinary capillaries. if an animal is at rest, no lymph flows from the hind limbs. to obtain a sample of limb lymph it is necessary to massage the limb. if, however, the veins to the limb be ligatured, we obtain a flow of lymph. the ligature of course causes a rise of the capillary pressure, and it has been argued that this rise of pressure starts a filtration through the capillary wall and hence a flow of lymph. but the stoppage of the blood-flow also damages the capillary wall and tissue cells by asphyxiation, and the resulting lymph-flow is in all probability the resultant of many complex processes. this case is analogous to the production of oedema in cases of heart disease where the circulation is feeble and the oxygen supply to the parts deficient. the results of these experiments form the main evidence in support of the filtration theory of lymph formation. they were first systematically studied by heidenhain, to whom we owe so much of our knowledge of lymph formation. he did not, however, conclude that they established the filtration theory. in continuing his observations heidenhain next studied the results following the injection of a number of substances into the blood. he found many which on injection gave rise to an increased lymph-flow from the thoracic duct, and arranged them in two classes. as instances of lymphogogues of the first class we may mention extract of mussels, leech extract, peptone, extract of crayfish muscle, extract of strawberries, of raspberries and many other like substances. lymphogogues of the second class comprise neutral salt solutions, urea, sugar, &c. considering the latter class first we may take as a type a solution of sodium chloride. injection of such a solution causes a large increase in the lymph-flow, and it has been proved that the lymph comes from the liver and intestines only--chiefly from the former. it is especially to be noted that there is no lymph-flow from the limbs, and the same is true for all lymphogogues of this class. as indicated above, the injection of a saline solution leads to a large and rapidly effected transport of fluid from the blood into muscle tissue, but though there is this large increase in tissue fluid, no lymph flows from the tissue. this result very powerfully disfavours the filtration theory of lymph formation. it practically refutes the idea that lymph formation is solely dependent upon such processes as filtration, osmosis and capillary permeability only. it brings out quite clearly that the exchange of fluid and dissolved salts, &c., between the blood and a tissue, and the flow of lymph from that tissue, are two separate and distinct processes, and especially that the first does not determine the second. also it is to be noted that the injection of a strong salt solution also excites a flow of duct lymph, again arising from the liver and intestines, but none from the limbs. in this instance, as previously stated, the muscles of the limbs are losing water, and so presumably are the liver and intestinal cells. this independence of tissue-blood exchange and lymph-flow is distinctly in favour of the view, which is rapidly gaining ground from histological observations, that in all instances the lymphatics commence in a tissue as closed capillary vessels. turning, in the next place, to the lymphogogues of the first class, it has been proved that the origin of this increase of flow is again from the liver. very many of the substances of this class are bodies which may when taken cause urticarial (nettle-rash) eruptions, a state which is generally regarded as being due to an action upon the capillary endothelium. their action as lymphogogues is also generally ascribed to an effect upon the capillary wall rendering it according to some more permeable, according to others leading to a direct secretory action on the part of the endothelium. we also know that many of the bodies of this class act upon the liver in other directions than in exciting an increased lymph production. thus they may cause an increase in bile secretion, or, as in the case of peptone, the liver cells may be excited to produce a new chemical material, in this instance an antithrombin. we have now to consider the effect of throwing an organ into activity upon the lymph-flow from the organ. in all cases in which it has been examined it is found that increased activity is accompanied by increased lymph-flow. thus, to take the instance of the submaxillary gland, which at rest does not discharge any lymph, stimulation of the chorda tympani is followed by a flow of lymph accompanying the flow of saliva simultaneously excited. the stimulation of the nerve also produces dilatation of the blood-vessels and therefore a rise in capillary pressure. but that this vascular change is not the factor determining the lymph-flow is proved by the administration of a small dose of atropine, which arrests the secretion without influencing the vascular reaction following chorda stimulation. after the atropine no lymph-flow occurs on stimulating the nerve. many other instances of a similar kind might be adduced. thus, we have seen that peptone specifically excites the liver cells and also causes an increased lymph-flow from the liver; or, as a last instance, the injection of bile salt excites a flow of bile and also excites a flow of lymph from the liver. the supporters of the filtration theory have argued that as activity of a tissue is necessarily accompanied by the discharge of metabolites from the active tissue cells, and as these are of small molecular size, they must set up an osmotic effect. water is therefore drawn into the tissue spaces, and this rise in fluid content results mechanically in a flow of lymph from the organ. the lymph simply drains away along the open lymphatics. this argument, however, loses all its force when we recall the fact that we may set up an enormous flow of fluid and salt into a tissue and its tissue spaces without causing the least flow of lymph. further, there is no reason to suppose that the metabolites discharged from a tissue during activity are produced in large quantities. the chief metabolite is undoubtedly carbonic acid, and this diffuses very rapidly and is quickly carried away by the blood. if, moreover, as is probably the case, the lymphatics commence as closed capillaries, we have a further difficulty in explaining how the fluid is driven through the lymphatic wall. either we must imagine the wall to be porous or there must be a greater pressure outside than inside, and it is very difficult to conceive how this is possible. as a general conclusion, then, it seems much more probable that we are here dealing with a secretory process, and that the active tissue produces some substance or substances--it may be carbonic acid--which throws the lymphatic capillary cells into activity. to sum up in a few words the present state of our knowledge as to lymph formation we may say that the exchange of water and salts between the blood and the tissues is probably entirely determined by processes of filtration and osmosis. further, that the physical condition of the capillary cells is frequently altered by many chemical substances, and that in consequence it may permit exudation into the tissue spaces much more freely. in the next place, the flow of lymph from a tissue is not solely determined by the amount of the tissue fluids. the lymph capillaries start as closed tubules, and the endothelial walls of these tubules play an active part (secretory) in determining when water and other substances shall be admitted into the capillary and further determine the quantity of such discharge. apparently, too, these cells are specifically excited when the tissue is thrown into activity, the exciting substance being a metabolite from the active tissue. leucocytes also are capable of passing through or between the endothelial cells of the lymph capillary. (t. g. br.) lymphatic system. in anatomy, the lymphatic system (lat. _lympha_, clear water) comprises the _lymphoid_ or _adenoid_ tissue so plentifully distributed about the body, especially in the course of the alimentary canal (see connective tissues), _lymph spaces_, _lymphatic vessels_ of which the lacteals are modifications, _lymphatic glands_, _haemolymph glands_, and the _thoracic_ and _right lymphatic ducts_ by which the lymph (q.v.) finally reaches the veins. _lymph spaces_ are mere spaces in the connective tissue, which usually have no special lining, though sometimes there is a layer of endothelial cells like those of the lymphatic and blood vessels. most of these spaces are very small, but sometimes, as in the case of the _sub-epicranial space_ of the scalp, the _capsule of tenon_ in the orbit, and the _retropharyngeal space_ in the neck, they are large and are adaptations to allow free movement. opening from these spaces, and also communicating with the serous membranes by small openings called stomata,[1] are the _lymph capillaries_ (see vascular system), which converge to the _lymphatic vessels_. these resemble veins in having an internal layer of endothelium, a middle unstriped muscular coat, and an external coat of fibrous tissue, though in the smaller vessels the middle coat is wanting. they have numerous endothelial valves, formed of two crescentic segments allowing the lymph to pass toward the root of the neck. when the vessels are engorged these valves are marked by a constriction, and so the lymphatics have a beaded appearance. the vessels divide and anastomose very freely, and for this reason they do not, like the veins, increase in calibre as they approach their destination. it is usual to divide the lymphatic vessels into a superficial and a deep set; speaking generally, the superficial ones are found near the course of the superficial veins, while the deeper ones accompany the arteries. probably any single drop of lymph passes sooner or later through one or more lymphatic glands, and so those vessels which are approaching a gland are called _afferent_, while those leaving are spoken of as _efferent lymphatics_. the _lacteals_ are special lymphatic vessels which carry the chyle from the intestine; they begin in lymphatic spaces in the villi and round the solitary and agminated glands, and pass into the mesentery, where they come in contact with a large number of _mesenteric glands_ before reaching the _receptaculum chyli_. the _lymphatic glands_ are pink bodies situated in the course of the lymphatic vessels, to which they act as filters. they are generally oval in shape and about the size of a bean, but sometimes, especially in the groin, they form irregular flattened masses 2 in. long, while, at other times, they are so small as almost to escape notice. they are usually found in groups. each gland has a fibrous capsule from which trabeculae pass toward the centre, where they break up and interlace, forming a network, and in this way a cortical and medullary region for each gland is distinguished; the intervals are nearly filled by lymphoid tissue, but close to the trabeculae is a lymph path or sinus, which is only crossed by the reticular stroma of the lymphoid tissue, and this probably acts as a mechanical sieve, entangling foreign particles; as an example of this the bronchial glands are black from carbon strained off in its passage from the lungs, while the axillary glands in a tattooed arm are blue. the blood-vessels enter at one spot, the _hilum_, and are distributed along the trabeculae. in addition to their function as filters the lymphatic glands are probably one of the sources from which the leucocytes are derived. the exact position of the various groups of glands is very important from a medical point of view, but here it is only possible to give a brief sketch which will be helped by reference to the accompanying diagram. in the head are found _occipital_ and _mastoid glands_ (fig. 1, [beta]), which drain the back of the scalp; _internal maxillary_ _glands_, in the zygomatic fossa, draining the orbit, palate, nose and membranes of the brain; _preauricular glands_ (fig. 1, [alpha]), embedded in the parotid, draining the side of the scalp, pinna, tympanum and lower eyelid; and _buccal glands_, draining the cheek region. in the neck are the _superficial cervical glands_ (fig. 1, [gamma]), along the course of the external jugular vein, draining the surface of the neck; the _submaxillary glands_ (fig. 1, [delta]), lying just above the salivary gland of the same name and draining the front of the face and scalp; the _submental glands_ (fig. 1, [epsilon]), beneath the chin, draining the lower lip, as well as sometimes the upper, and the front of the tongue; the _retropharyngeal glands_, draining the naso-pharynx and tympanum; the _pretracheal glands_, draining the trachea and lower part of the thyroid body; and the _deep cervical glands_, which are by far the most important and form a great mass close to the internal jugular vein; they receive afferent vessels from most of the glands already mentioned and so are liable to be affected in any trouble of the head or neck, especially of the deeper parts. into them the lymphatics of the brain pass directly. the lower part of this mass is sometimes distinguished as a separate group called the _supra-clavicular glands_, which drain the back of the neck and receive afferents from the occipital and axillary glands. the efferents from the deep cervical glands join to form a common vessel known as the _jugular lymphatic trunk_, and this usually opens into the thoracic duct on the left side and the right lymphatic duct on the right. [illustration: fig. 1.--superficial lymphatic vessels and glands. [alpha], preauricular. [beta], mastoid. [gamma], superficial cervical. [delta], submaxillary. [epsilon], submental. [zeta], infraclavicular. [eta], anterior axillary. [theta], supratrochlear. [iota], antecubital. [kappa], inguinal. [lambda], superficial femoral.] in the thorax are found _intercostal glands_ (fig. 2, i.), near the vertebral column draining the back of the thoracic walls and pleura; _internal mammary glands_, draining the front of the same parts as well as the inner part of the breast and the upper part of the abdominal wall; _diaphragmatic glands_, draining that structure and the convex surface of the liver; _anterior, middle, posterior and superior mediastinal glands_, draining the contents of those cavities. the _bronchial glands_, draining the lungs, have already been referred to. in the abdomen and pelvis the glands are usually grouped round the large arteries and are divided into visceral and parietal. among the visceral are the _gastric glands_, draining the stomach (these are divided into _coronary_, _subpyloric_ and _retropyloric_ groups); the _splenic glands_ at the hilum of the spleen, draining that organ, the tail of the pancreas and the fundus of the stomach; the _hepatic glands_ in the small omentum, draining the lower surface and deep parts of the liver; the _pancreatic glands_, behind the lesser sac of the peritoneum, draining the head and body of the pancreas, the _superior mesenteric glands_; from one to two hundred in number, lying in the mesentery and receiving the lacteals; the _ileo-caecal glands_, draining the caecum, one of which is known as the _appendicular_ gland and drains the vermiform appendix and right ovary; the _colic glands_ along the right and middle colic arteries, draining the ascending and transverse colon; the _inferior mesenteric glands_ in the course of that artery, draining the descending iliac and pelvic colons; the _rectal_ glands, behind the rectum, draining its upper part. among the parietal glands are the _external iliac glands_, divided into a lateral and mesial set (see fig. 2, e.i.), and receiving the inguinal efferent vessels and lymphatics from the bladder, prostate, cervix uteri, upper part of the vagina, glans penis vel clitoridis and urethra. the _supra_ and _infra-umbilical glands_ receive the deep lymphatics of the abdominal wall, the former communicating with the liver, the latter with the bladder. from the latter, vessels pass to the epigastric gland lying in front of the termination of the external iliac artery. the _internal iliac glands_ (fig. 2, i. i.) are situated close to the branches of this artery and drain the rectum, vagina, prostate, urethra, buttock and perinaeum. _common iliac glands_ (fig. 2, c.i.) lie around that artery and receive afferents from the external and internal iliac glands as well as a few from the pelvic viscera.[2] the _aortic glands_ are grouped all round the length of the aorta, and are divided into _pre_-, _retro_- and _lateral aortic_ groups (fig. 2 p.a. and l), all of which communicate freely. the upper preaortic glands are massed round the coeliac axis, and receive afferents from the gastric, hepatic, splenic and pancreatic glands; they are known as _coeliac glands_. the _lateral aortic glands_ drain the kidney, adrenal, testis, ovary, fundus of uterus and lateral abdominal walls. in the upper extremity a few small glands are sometimes found near the deep arteries of the forearm. at the bend of the elbow are the _ante-cubital_ glands (fig. 1 [lambda]) and just above the internal condyle, one or two _supra-trochlear glands_ (fig. 1, [theta]). the _axillary glands_ (fig. 1, [eta]) are perhaps the most practically important in the body. they are divided into four sets: (1) _external_, along the axillary vessels, draining the greater part of the arm; (2) _anterior_, behind the lower border of the pectoralis major muscle, draining the surface of the thorax including the breast and upper part of the abdomen; (3) _posterior_ along the subscapular artery, draining the back and side of the trunk as low as the umbilical zone; (4) superior or _infra-clavicular glands_ (fig. 1, [zeta]), receiving the efferents of the former groups as well as lymphatics accompanying the cephalic vein. in the lower limb all the superficial lymphatics pass up to the groin, where there are two sets of glands arranged like a t. the _superficial femoral_ glands (fig. 1, [lambda]) are the vertical ones, and are grouped round the internal saphenous vein; they are very large, drain the surface of the leg, and are usually in two parallel rows. the _inguinal glands_ form the cross bar of the t (fig. 1, [kappa]), and drain part of the buttock, the surface of the abdomen below the umbilicus and the surface of the genital organs. the deep lymphatics of the leg drain into the _anterior tibial gland_ on that artery, the _popliteal glands_ in that space, and the _deep femoral glands_ surrounding the common femoral vein. [illustration: from a. m. paterson, cunningham's _text-book of anatomy_. fig. 2.--deep lymphatic glands and vessels of the thorax and abdomen (diagrammatic). afferent vessels are represented by continuous lines and efferent and interglandular vessels by dotted lines. c. common iliac glands. c.i. common intestinal trunk. d.c. deep cervical glands. e.i. external iliac glands. i. intercostal glands and vessels. i.i. internal iliac glands. l. lateral aortic glands. m. mediastinal glands and vessels. p.a. pre-aortic glands and vessels. r.c. receptaculum chylii. r.l.d. right lymphatic duct. s. sacral glands. s.a. scalenus anticus muscle. t.d. thoracic duct.] the _thoracic duct_ begins as an irregular dilatation known as the _receptaculum chyli_, opposite the first and second lumbar vertebrae, which receives all the abdominal lymphatics as well as those of the lower intercostal spaces. the duct runs up on the right of the aorta through the posterior mediastinum and then traverses the superior mediastinum to the left of the oesophagus. at the root of the neck it receives the lymphatics of the left arm and left side of the neck and opens into the beginning of the left innominate vein, usually by more than one opening. the _right lymphatic duct_ collects the lymphatics from the right side of the neck and thorax, the right arm, right lung, right side of the heart and upper surface of the liver; it is often represented by several ducts which open separately into the right innominate vein. _haemolymph glands_ are structures which have only been noticed since 1884. they differ from lymphatic glands in their much greater vascularity. they assist the spleen in the destruction of red blood corpuscles, and probably explain or help to explain the fact that the spleen can be removed without ill effects. in man they extend along the vertebral column from the coeliac axis to the pelvis, but are specially numerous close to the renal arteries. t. lewis suggests that lymphatic and haemolymph glands should be classified in the following way:-- / haemal glands. / simple. | \ specialized (spleen) | haemolymph | / 1. blood and lymph sinuses glands. < haemal lymphatic < separate. | glands. | 2. blood lymph sinuses. | \ 3. other combined forms. | \ lymphatic glands. details and references will be found in papers by t. lewis, _j. anat. & phys._ vol. xxxviii. p. 312; w. b. drummond, _journ. anat. and phys._ vol. xxxiv. p. 198; a. s. warthin, _journ. med. research_, 1901, p. 3, and h. dayton, _am. journ. of med. sciences_, 1904, p. 448. for further details of man's lymphatic system see _the lymphatics_ by delamere, poirier and cuneo, translated by c. h. leaf (london, 1903). _embryology._--the lymphatic vessels are possibly developed by the hollowing out of mesenchyme cells in the same way that the arteries are; these cells subsequently coalesce and form tubes (see vascular system). there is, however, a good deal of evidence to show that they are originally offshoots of the venous system, and that their permanent openings into the veins are either their primary points of communication or are secondarily acquired. the lymphatic and haemolymph glands are probably formed by the proliferation of lymphocytes around networks of lymphatic vessels; the dividing lymphocytes form the lymphoid tissue, and eventually the network breaks up to form distinct glands into which blood vessels penetrate. if the blood vessels enlarge more than the lymphatic, haemolymph glands result, but if the lymphatic vessels become predominant ordinary lymphatic glands are formed. at an early stage in the embryo pig two thoracic ducts are formed, one on either side of the aorta, and the incomplete fusion of these may account for the division often found in man's duct. in the embryo pig too there have been found two pairs of lymph hearts for a short period. see a. s. warthin, _journ. med. research_, vol. vii. p. 435; f. r. sabin, _am. journ. of anat._ i., 1902; and, for literature, _development of the human body_, by j. p. mcmurrich (london, 1906), and quain's _anatomy_ (vol. i., london, 1908). _comparative anatomy._--a lymphatic system is recognized in all the craniata, and in the lower forms (fishes and amphibia) it consists chiefly of lymph spaces and sinuses in communication with the coelom. in fishes, for instance, there is a large _subvertebral lymph sinus_ surrounding the aorta and another within the spinal canal. in amphibia the subvertebral sinus is also found, and in the anura (frogs and toads) there is a great _subcutaneous lymph sinus_. _lymph hearts_ are muscular dilatations of vessels and are found in fishes, amphibians, reptiles and bird embryos, and drive the lymph into the veins; they are not known in adult mammals. in birds the thoracic duct is first recognized, and opens into both right and left precaval veins, as it always does in some mammals. in birds, however, some of the lymphatics open into the sacral veins, and it is doubtful whether true lymphatic glands ever occur. in birds and mammals lymphatic vessels become more definite and numerous and are provided with valves. haemolymph glands are present in mammals and birds, but have not been seen lower in the scale, though s. vincent and s. harrison point out the resemblance of the structure of the head kidney of certain teleostean fishes to them (_journ. anat. and phys._ vol. xxxi. p. 176). for further details see _comparative anat. of vertebrates_, by r. wiedersheim (london, 1907). (f. g. p.) _diseases of the lymphatic system and ductless glands._ _lymphadenitis_ or inflammatory infection of the lymphatic glands, is a condition characterized by hyperaemia of and exudation into the gland, which becomes reader, firmer and larger than usual. three varieties may be distinguished: simple, suppurative and tuberculous. the cause is always the absorption of some toxic or infective material from the periphery. this may take place in several of the acute infectious diseases, notably in scarlet fever, mumps, diphtheria and german measles, or may be the result of poisoned wounds. the lymphatic glands are also affected in constitutional diseases such as syphilis. simple lymphadenitis usually subsides of its own accord, but if toxins are produced in the inflamed area the enlargement is obvious and painful, while if pyogenic organisms are absorbed the inflammation progresses to suppuration. _tuberculous lymphadenitis_ (scrofula) is due to the infection of the lymph glands by koch's tubercle bacillus. this was formerly known as "king's evil," as it was believed that the touch of the royal hand had power to cure it. it occurs most commonly in children and young adults whose surroundings are unhealthy, and who are liable to develop tuberculous disease from want of sufficient food and fresh air. some local focus of irritation is usually present. the ways in which the tubercle bacillus enters the body are much disputed, but catarrh of the mucous membranes is regarded as a predisposing factor, and the tonsils as a probable channel of infection. any lymphoid tissue in the body may be the seat of tuberculous disease, but the glands of the neck are the most commonly involved. the course of the disease is slow and may extend over a period of years. the earliest manifestation is an enlargement of the gland. it is possible in this stage for spontaneous healing to take place, but usually the disease progresses to caseation, in which tuberculous nodules are found diffused throughout the gland. occasionally this stage may end in calcification of the caseous matter, the gland shrinking and becoming hard; but frequently suppuration follows from liquefaction of the caseating material. foci of pus occur throughout the gland, causing destruction of the tissue, so that the gland may become a single abscess cavity. if left to itself the abscess sooner or later bursts at one or several points, leaving ulcerated openings through which a variable amount of pus escapes. temporary healing may take place, to be again followed by further breaking down of the gland. this condition, if untreated, may persist for years and may finally give rise to a general tuberculosis. the treatment consists mainly in improving the general health with good diet, fresh air (particularly sea air), cod-liver oil and iron, and the removal of all sources of local irritation such as enlarged tonsils, adenoids, &c. vaccination with tuberculin (tr) may be useful. suppuration and extension of the disease require operative measures, and removal of the glands _en masse_ can now be done through so small an opening as to leave only a very slight scar. in _tabes mesenterica_ (tuberculosis of the mesenteric glands), usually occurring in children, the glands of the mesentery and retroperitonaeum become enlarged, and either caseate or occasionally suppurate. the disease may be primary or may be secondary to tuberculous disease of the intestines or to pulmonary phthisis. the patients are pale, wasted and anaemic, and the abdomen may be enormously enlarged. there is usually moderate fever, and thin watery diarrhoea. the caseating glands may liquefy and give rise to an inflammatory attack which may simulate appendicitis. limited masses are amenable to surgical treatment and may be removed, while in the earlier stages constitutional treatment gives good results. tuberculous peritonitis frequently supervenes on this condition. _lymphadenoma_ (hodgkin's disease), a disease which was first fully described by hodgkin in 1832, is characterized by a progressive enlargement of the lymphatic glands all over the body, and generally starts in the glands of the neck. the majority of cases occur in young adults, and preponderate in the male sex. the first symptom is usually enlargement of a gland in the neck, with generally progressive growth of the glands in the submaxillary region and axilla. the inguinal glands are early involved, and after a time the internal lymph glands follow. the enlargements are at first painless, but in the later stages symptoms are caused by pressure on the surrounding organs, and when the disease starts in the deeper structures the first symptoms may be pain in the chest and cough, pain in the abdomen, pain and oedema in the legs. the glands may increase until they are as large as eggs, and later may become firmly adherent one to another, forming large lobulated tumours. increase of growth in this manner in the neck may cause obstructive dyspnoea and even death. in the majority of cases the spleen enlarges, and in rare instances lymphoid tumours may be found on its surface. anaemia is common and is secondary in character; slight irregular fever is present, and soon a great and progressive emaciation takes place. the cases are of two types, the acute cases in which the enlargements take place rapidly and death may occur in two to three months, and the chronic cases in which the disease may remain apparently stationary. in acute lymphadenoma the prognosis is very unfavourable. recovery sometimes takes place in the chronic type of the disease. early surgical intervention has in some cases been followed by success. the application of x-rays is a valuable method of treatment, superficial glands undergoing a rapid diminution in size. of drugs arsenic is of the most service, and mercurial inunction has been recommended by dreschfeld. organic extracts have of late been used in the treatment of lymphadenoma. _glandular fever_ is an acute infectious fever, generally occurring in epidemics, and was first described by e. pfeiffer in 1889. it usually affects children and has a tendency to run through all the children of a family. the incubation period is said to be about 7 days. the onset is sudden, with pain in the neck and limbs, headache, vomiting, difficulty in swallowing and high temperature. on the second day, or sometimes on the first, swelling of the cervical glands is noticed, and later the posterior cervical, axillary and inguinal glands become enlarged and tender. in about half the cases the spleen and liver are enlarged and there is abdominal tenderness. west found the mesenteric nodes enlarged in 37 cases. nephritis is an occasional complication, and constipation is very usual. the disease tends to subside of itself, and the fever usually disappears after a few days; the glandular swellings may, however, persist from one to three weeks. considerable anaemia has been noticed to follow the illness. rest in bed while the glands are enlarged, and cod-liver oil and iron to meet the anaemia, are the usual treatment. _status lymphaticus_ (lymphatism) is a condition found in children and some adults, characterized by an enlargement of the lymphoid tissues throughout the body and more particularly by enlargement of the thymus gland. there is a special lowering of the patient's powers of resistance, and it has been said to account for a number of cases of sudden death. in all cases of status lymphaticus the thymus has been found enlarged. at birth the gland (according to bovaird and nicoll) weighs about 6 grammes, and does not increase after birth. in lymphatism it may weigh from 10 to 50 grammes. the clinical features are indefinite, and the condition frequently passes unrecognized during life. in most cases there is no hint of danger until the fatal syncope sets in, which may be after any slight exertion or shock, the patient becoming suddenly faint, gasping and cyanosed, and the heart stopping altogether before the respirations have ceased. the most trifling causes have brought on fatal issues, such as a wet pack (escherich) or a hypodermic injection, or even a sudden plunge into water though the head is not immersed. the greater number of deaths occur during the administration of anaesthetics, which seem peculiarly dangerous to these subjects. when an attack of syncope takes place no treatment is of any avail. virchow, west and goodhardt have described a form of asthma in adults which they ascribe to a hypertrophied thymus gland and term "thymic asthma." _diseases of the spleen._--physiological variations and abnormalities and absence of the spleen are so rare as to require no comment. the most usual pathological condition which gives rise to symptoms is that of _wandering spleen_, which may or may not be secondary to a wandering left kidney. it may produce symptoms of dragging and discomfort, dyspepsia, vomiting and abdominal pain, and sometimes jaundice (treves), or the pedicle may become twisted, producing extremely severe symptoms. the treatment is entirely surgical. abscess in the spleen occasionally occurs, usually in association with infective endocarditis or with general pyaemia. the spleen may be the seat of primary _new growths_, but these are rare, and only in a small portion of cases does it share in the metastatic reproduction of carcinoma. infection of the spleen plays a prominent part in many diseases, such as malaria, typhoid fever, lymphadenoma and leucaemia. diseases of the thyroid gland (see goitre) and _addison's disease_ (of the suprarenal glands) are treated separately. (h. l. h.) footnotes: [1] it has recently been stated that stomata do not exist in the peritoneum. [2] for further details of the pelvic glands see "seventh report of the committee of collective investigation," _journ. anat. and phys._ xxxii. 164.