PUBLIC HEALTH

the main object should be to prevent disease rather than to cure it. the one is easy and cheap, the other difficult, expensive and often impossible. as the open air sanatorium does so much for the rickety and tubercular, this should be the model for the bringing up of all children. the open air school with the floor gently heated—as the ancient romans heated floors by the hypocaust—should replace the indoor schools, while factories should move to garden cities as far as possible and have attached playing fields and allot- ments for gardening. ventilation probiems.—for air to feel fresh it must have such cooling and evaporative power as suffices to keep the head pleasantly cool and the skin free from sensible perspiration. movement of the air is of great importance, because it prevents stagnation of air which is made warm and humid by the body and is entangled in the clothing, and greatly promotes loss of heat from the skin by convection and evaporation. in occupied rooms not contaminated by coal-gas leaks or poisonous fumes arising from manufacturing processes, natural ventilation, sct up by differences of temperature inside and outside, suffices to keep the air chemically pure enough, even though all doors and windows are shut. there is normally § to 6°% of carbon dioxide and 143° of oxygen in the depths of the lungs, and the physio- logical regulation of breathing is such as to keep these amounts constant. increase of carbon dioxide or diminution of oxygen, which in the worst ventilated rooms does not amount to more than $°% has then no effect. the importance of keeping the percentage of carbon dioxide in rooms very low is to insure a ventilation sufficient to cool the body and evaporate moisture from it and to keep down the number of dust particles and microbes exhaled by carriers of catarrhal or other diseases. most uncomfortable conditions due to heat stagnation may be found when chemical purity of the air is very high, and comfortable conditions, e.g., in a submarine cooled by the sea, when owing to long submergence chemical purity is worst. the amount of oxygen breathed in each pint of air is much lower at alpine health resorts owing to the tenuity of the air at great heights, than in stuffy, crowded rooms in a city on the plains—a further proof, if it were wanted, that the slight diminution of oxygen percentage in such rooms ts of no importance. the commonly accepted opinion that there ate chemical poisons in exhaled air has been negatived by exact experiment. stuffy air of crowded reoms is contaminated with ,microbes cx- plosively exhaled from the respiratory passages in coughing, sneezing and speaking, and dust from soiled clothes. such mi- crobes directly inhaled by others may disseminate catarrhs, sore throats, tuberculosis of the lung, etc. the number of such microbes is very greatly reduced by open window ventilation. in several schools ventilated by the plenum system time lost by children through catarrhs was on the average six times greater than in a school ventilated by open windows. confined air of rooms is also greatly polluted with dust stirred up by people, and in cities with soot. some dusts, such as free silica and lead, are poisonous, and have a most deleterious effect. the breathing of free silica dust by tin and gold miners, by sand- stone, granite, and flint workers, and by gritstone grinders causes slow degeneration of the lung, ending generally in a tubercular infec- tion. the death-rate from tuberculosis in such workers has been extremely high, and special precautions against dust must be taken public health to jower it (see miners’ putirsis). the breathing of chalk, coal, and animal or vegetable dust such as bone meal and flour are rela- tively harmless, but may produce shortness of breath in later middle life. some people are hypersensitive to certain animal or vegetable dusts and get hay fever or asthma from breathing such, e.g., from dandruff of horses, dogs, cats, from dust of feathers, from pollen of grasses, from spores cf moulds such as aspergillus. they are relieved by going to dust-free places as in the alps, or to sea, or by sleeping in a special dust free room. the inhaled air is exhaled, heated up to almost body tempera- ture and saturated with water by the respiratory membrane. it is important for the health of this membrane that it should receive an ample supply of arterial blood and lymph, and secrete plenty of fluid to cleanse itself, with the aid of its ciliated epithelium, of dust and microbes. cool air contains very little moisture, even when saturated, and can take up much from the lungs and so act favourably compared with the warm moist air of crowded, stufiy rooms. the natural conditions which pertain out of doors are a cool breeze moving round the head and the feet kept warm by the ground. in stuffy, artificially heated rooms there is a draught on the floor while the head is surrounded with warm, stagnant air. as a result, the nasal membrane becomes congested, the alr-way through the nose constricted, and stuffy feelings and headache are occasioned. warming the feet and cooling the bead by a fan at once relieves these feelings. while there is no evidence that ‘ionisation ” of the air has any influence on our feeling or health, the adequate cooling of the body is most important in keeping up the tone of the muscles and the body heat production. the body should be stimulated to keep up its own heat by com- bustion of food, and the “ fire of life’ kept burning actively. greater depth of breathing, more active circulation of blood, better appetite, digestion and absorption of food result; con- stipation is avoided by greater muscular tone and the deeper breathing induced by exercise taken to keep warm, and the bowels are kept clear of bacterial poisons owing to the more com- plete use of food, and more active circulation through and tone of their walls. general health and resistance to disease are thus promoted. warm, moist atmospheres lower working efficiency and vigorous health. the body heat production of native students in singapore is not more than half that of an athletic english student. the native of singapore can do very little work. (see heating and ventilation.) food problems.—lll-nutrition may arise because food is de- ficient in energy value or in quality, or because the environment depresses the fire of life and reduces the healthy action of the bowels and the appetite, or because the body is over-fatigued, and the expenditure of nerve energy leaves insufficient for the digestive and absorptive functions. those who carry out in factories skilled hand operations seem more liable to illness than heavy workers, ¢.g., coal-miners, smiths and foundry men ancl agriculturists. the skilled hand-workers lead a far more caged life, using their hand muscles to make many small, fine move- ments, not using their big body and leg muscles, not breathing deeply, not having a high rate of food oxidation. the chest is fixed to make skilled hand movements, and this modifies their breathing. the number of fine skilled movements they have to make brings about nervous fatigue, while, their food oxidation being relatively low, and breathing shallow, ithe onset of fatigue is not resisted as it should be by a high rate of nutrition. the relatively warm environment brings too much blood into the skin of the factory workers, and does not tone up the body as the open air life docs. infection with catarrhal complaints is far more spread among them, and their respiratory membrane is not kept in a healthy state as it is in those who deep-breathe cool, dry air. children who are over-crammed for examinations come under this category, so too college students and clerks. in some occupations 40° of the workers may be away from work each year for some period owing to sickness, while the number of cases seeking medical relief may number 100°% of the workers or even more each year. publig: health housing problems.—millions live in one to three-roomed tenements, and the cinema and a sensational press take the place of fun and frolic in the open air. the crowded life of the tenement lowers the vitality and exhausts the nervous system. ill-feeding comes on top of this, the workers having no garden to give them fresh vegetable foods. an enormous economic loss results from their having no chance of spending their leisure hours in gardening and in improving their homes. civilisedl man has to have a book some hundreds of pages long merely to catalogue his diseases. mccarrison describes in the remote himalayas a tribe of magnificent physique, amongst whom there is no dyspepsia or neurasthenia, no gastric or duodenal ulcers, no appendicitis or mucous colitis, little or no cancer. food requirements we must have in our food, first, sufficient fuel value, or energy, to keep up our body heat and to do muscu- lar work on. next we must have proteins which will yield us on digestion all those amino-acids into which proteins are split on digestion, which are required to build our tissue, and to secure these we want variety of both animal and vegetable proteins. some proteins, for example, zein in maize, fail in one or other of the required constituents, and disease results from restriction tosuch. then we need carbohydrates and fats, mainly to provide fuel, but also to help build body substance. in addition, we must have certain salts, and particularly chloride and phosphate of sodium, potassium, calcium and magnesium with traces of iron and iodine, on which the processes of life intimately depend. lastly, the food must contain vitamines (q.z.), traces of certain vital substances which have hitherto not been separated but are known to exist by feeding experiments. the vitamines have been compared with the sparks which fire the petrol in a motor engine. a mixed diet of fresh meat, milk, butter, eggs, fruits, honey, molasses, vegetables and wholemeal bread, such as our ancestors ate, supplied all, but now this food is largely replaced by the products of the miller and canner, by white bread and polished white rice, cornflour, sago, tapioca, tinned meat, sterilised milk, sugar, margarine made out of nuts, egg substitutes, tinned or bottled fruits. tea, sugar, white bread, margarine, and low- quality jam are the staple foods of the very poor. the effect of preservatives and refining processes has been to lessen the vita- mines and essential salts, often with disastrous effect to growth, health and breeding power. now, the growing of salads, which might be possible in gardens and courts, in window boxes and on roofs in cities, is stopped by smoke pollution; this, too, damages the fields, gardens and allotments, and lessens the supply of vegetable food and of milk of cows fed on fresh young grass, and makes these things costly to city people (see smoke prevention). solar radiation—the radiant energy of the sun tempered by the atmosphere keeps going the manifestations of life. plants energised by the sun, and using, as a transformer of energy, the green chlorophyll, build up their substance out of inorganic materials. this substance is the food of the animal world. modern theory suggests that all chemical change, vital and non- vital, is touched off by radiant energy, by light or heat, and that the speed of such change is determined by the intensity of radiation. the sun rays which are most active on living cells, killing these if too strong, are those beyond the violet, insensible to us, and called ultra-violet. these rays act also most power- fully on a sensitised photographic film. the visible rays, in part reflected from the skin, in part penetrate and are absorbed by the cutaneous blood and warm that. they are absorbed by the epidermis and scarcely penetrate to the blood beneath. the red rays penetrate through to deeper tissues and warm these. the skin can stand, without being scorched, twice as much radiant energy per unit of time in the form of visible sun rays as it can of dark heat rays, because the visible rays largely penetrate, and, warming the blood locally, are carried away as heat to cooler parts of the body. the dark heat rays, absorbed by the surface of the skin, make us feel warm and stufiy indoors. out of doors, on the other hand, the blood circulating in the naked skin is warmed by the sun which penetrates to it, while the surface of the skin is fanned and cooled by the breeze (sce heliotherapy). 261 the biologically active ultra-violet rays are filtered off by glass. exposure in rooms lighted by windows is not the same as exposure to light out of doors. in heating our rooms with hot water and steam pipes we expose ourselves to infra-red rays; fires give us chiefly infra-red and visible rays; incandescent elec- tric light visible rays. a coal fire fouls the sky with smoke and cuts off sunlight; we must, therefore, take to gas or smokeless fuel fires. these and open windows give us the most healthful conditions. the dark heat of steam pipes and the stagnant warm air of shut-up rooms depress health, expose us to a more massive infection, and make us less resistant to catarrh, pneu- monia, etc. over-heating of tubercular, and particularly febrile, patients should be avoided. exposure should not be in hot sun boxes, but in cool open air and to sky-shine or early morning direct sun. sunstroke.—sunstroke may be caused by local heating of the head, while heat stroke results from heating the whole body through failure of the sweat mechanism. a wet sheet and a fan supplying this mechanism artificially prevent heat stroke. sunburn of the skin is not produced by the high sun, which on clear days contains rays with a wave-length as short as 300- 295 millionths of a millimetre; but ultra-violet rays with wave- length of 310-300 wy, if intense enough, may produce severe sunburn, and it is these rays which act most in the english atmosphere, with its high content of dust, smoke and vapour. with arc lamps, probably no rays shorter than 240 pu penetrate the horny layer of the skin; but such short rays penetrate into and are absorbed by microbes and kill them. according to modern physical theory, the ultra-violet rays act in quanta and displace electrons from their orbits in the atoms. this sects up, in living cells of the epidermis and in nerve endings which lie among these, a secondary molecular chemical action, which after a latent period produces erythema, oedema, etc. only those rays which are absorbed by the living substance have action. the various artificial sources of ultra-violet radiation, carbon arc, mercury vapour, lamps, etc., have an effect on the skin similar to the sun, the amount of subsequent pigmentation depending on the intensity and depth of penetration of the ultra- violet rays. the haemobactericidal power of the blood, tested in vitro, usually increases when the dose of ultra-violet radiation is sufficient to produce erythema. the area of skin which has to be exposed to produce this effect is not large. excessive sun- burn damage is harmful, a small amount stimulating and useful. if the body is fighting an acute disease, reactions in the skin set up by irradiation may be harmful, while most useful in chronic infections and states of debility. the brown pigment, melanin, which forms in particles within the cells of the epidermis, acts as a screen protecting the epider- mic cells and the blood from over-radiation. by absorbing and converting rays into heat, melanin brings about stimulation of the nerve endings in the epidermis, and this excites sweating, which in its turn protects from over-heating. some immunity to a second exposure is set up in the epidermis of a white person within a few hours after irradiation, and long before pigmentation takes place. this is due to a thickening of the horny cells, which a few days later peels off. just after desquamation the skin is again sensitive. ‘these facts are borne in mind when arranging the periods of light treatment. in the choice of a garment, if any is to be worn during light treatment, an artificial silk made of acetyl cellulose, thin and open-meshed, screens off least ultra-violet rays, but with even such the loss may be 50 per cent. smoke pollution.—window glass, clothing and smoke pollu- tion screen off almost all ultra-violet radiation from citizens in winter, and their food is deficient in vitamins. hence the devclop- ment of rickets and depression of health in winter. owing to smoke pollution in big cities, the ultra-violet rays are cut down to one-third of the value which pertains in clean country places. every effort should be made to prevent smoke pollution and iu secure adequate exposure of the skin to ultra-violet rays. while securing the use of smokeless fuel, arc lamp baths should be instituted not only in hospitals but in schools and public 262 baths. round a long-flame arc taking 2 to 3 kilowatts with “white flame ” carbon poles (metal cored), and fitted with a wire screen a yard away, children could sit for 10 minutes, wear- ing only a loin cloth. two such baths a week in winter would work great good as a preventive of rickets, tuberculosis, rheu- matic fever, catarrhs, skin diseases, etc., and as a stimulator of vigour. goggles must be worn and a trained nurse be at hand. modern hospitals.—to build brick hospitals is out of date; all hospitals should be one-storeyed bungalows with wide verandahs, the beds can then run easily from the ward to the verandah and to the open court outside. nurses must be suitably dressed so as to enjoy the open air life. only receiving stations should be in cities, with ambulances to convey patients to the bungalow hospitals in the open country. open air and ultra- violet radiation should be used to prepare patients for operation and to hasten their cure after operation. it has been asserted that artificial light treatment cannot approach heliotherapy in curative effect. by the wise use of arc lights and suflicient ex- posure to open air and good feeding, progressive cure of surgical tuberculosis can be brought about in winter even in our english cities. to eliminate tuberculosis from cattle, the shutting up in badly ventilated dark byres should be prohibited. cattle no less than children might be given arc light baths in winter. bibliography.—c. g. moor and e. a. cooper, field sanitation (1918); league of nations, exropean heulth conference ileld at warsaw, march 20 to 28 1922 (1922); medical research council, special report no. 60, use of death-rates as a measure of h yeienic conditions (1922); ralph e. blount, health, public and personal (1922); v. c. vaughan, epidemiology and public health, 3 vol. (1922); l. c. parkes and h. r. kenwood, iygiene and public health (1923); jean broadhurst, home and community hygiene (2nd ed., 1923); b. n. ghosh, a treatise on hygiene and public health, with special reference to the tropics (5th ed., 1924); mark f. boyd., pre- ventive medicine (2nd ed., 1925); e. b. phelps, the principles of public health engineering (1925); carlos e. p. soldau, al servicio de la higien americana (1925); seneca egbert, a manual of hygiene and sanitation (8th ed., 1926); h. h. waite, disease prevention (1926). (l. e. h.) publicity: see advertising. public schools.—the claim made for the public schools, using this term in the english not the american sense, that, whatever their shortcomings may be, they are at any rate suc- cessful in producing sound character and public spirit was put to a severe test on the outbreak of war in 1914 and triumphantly sustained. not only did the old boys at once join the colours in large numbers, but the boys who should have returned for another school year enlisted freely, and every public school reassembled in sept. 1914 with numbers much depleted. of those who served, one in every five fell, and the rolls of honour with strik- ing similarity generally contain as many names as there are boys in the school. during the war, owing to the loss of many masters, and the lack of the leadership of boys over 18, the work of the schools was carried on with increasing difficulty. but their tone continued sound, and the boys maintained the standard surpris- ingly, considering the demands made upon their time by inten- sive military training and the disturbing effect of the near pros- pect of active service. contrary to general expectation, the schools emerged from the war filled to overflowing, and with waiting-lists so long that places could clearly not be found for all the aspirants. this was due to the success in leadership of boys trained in the schools, to an increased sense in the nation at large of the value of education, and particularly this form of education, and to a wider diffusion of wealth, which made possible a public school course for the sons of many who would not have been able to afford it before. since 1918 the schools have remained full. stowe, canford and others have been opened to meet the demand, and there is probably room for more. these years have seen a profound change in the curriculum and outlook of the public schools, of which the most striking sign has been the abolition of compulsory greek at oxford and cambridge. this has, however, not been followed by the disappearance of classical studies (see classical education); on the con- publicity—publishing trary, they are again increasing in favour. the certificate exam- iners of that authority which examines most of the public schools reported 830 candidates in the summer of 1923, 981 in 1924 and 1,087 in 1925, in the school certificate only, and nearly all these are serious students. the school certificate itself is the most important development of the years under review. its basic principle is that it is the business of the schools to give a general education in which (a) english and allied subjects, (6) a foreign language or languages, (c) mathematics and science shall be represented, though science has not established itself as a com- pulsory subject. it is designed for average boys of 16, and it is assumed that till then boys follow approximately the same course of study. the examination, when passed in the right subjects at a sufficient standard, admits to matriculation at the universities, and to entrance into most of the professions (see examinations). the new system has undoubtedly had a marked effect in improv- ing the work of the average boy, in giving a new spirit not only to him but to his teachers, and in rendering impossible the exist- ence of whole classes of boys, who, being without object, and without heart, were often made the reproach of the schools in the past. to bring the army examination into line with this system, candidates without a school certificate are not at present allowed to sit. - to boys above this level the schools offer to-day a greater variety of advanced courses and a greater choice of intellectual interests. science has come greatly to the fore, and aesthetic studies, particularly music, have advanced considerably and will probably make still greater claims in the future. though the public schools were never more popular than they are to-day, they are nevertheless segregated. their masters stand outside the national pension scheme; they seldom transfer from school to school; the schools themselves are accessible to a limited class only. these are privileges not without their dangers. (c.n.)