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Tuberculosis

TUBERCULOSIS. The word " tuberculosis," as now used, signifies invasion of the body by the tubercle bacillus, and is applied generally to all morbid conditions set up by the presence of the active parasite. The name is derived from the " tubercles " or " little lumps " which are formed in tissues invaded by the bacillus; these were observed and described long before their real nature or causation was known. (For an account of the organism, which was discovered by Koch in 1882, see PARASITIC DISEASES.) The bacillus attacks every organ and tissue of the body, but some much more frequently than others. The commonest seats of tuberculous disease are the lungs, lymphatic glands, bones, serous membranes, mucous membranes, intestines and liver. Before the discovery of the bacillus its effects in different parts of the body received separate names and were classified as distinct diseases. For instance, tuberculosis of the lung was called " consumption " or " phthisis," of the bones and lymphatic glands " struma " or " scrofula," of the skin " lupus," or the intestinal glands " tabes mesenterica." Some of these names are still retained for convenience, but the diseases indicated by them are known to be really forms of tuberculosis. On the other hand, there are " tubercles " which are not caused by the tubercle bacillus, but by some other source of irritation, including various parasitic organisms, some of which closely resemble the tubercle bacillus. To these forms of disease, which are not as yet well understood, the term pseudo-tuberculosis has been given. Lastly, the word " tubercular " is still sometimes applied to mere lumpy eruptions of the skin, which have no connexion with tuberculosis or pseudo-tuberculosis.

Pathology. The effects of tuberculosis on the structures attacked vary greatly, but the characteristic feature of the disease is a breaking-down and destruction of tissue. Hence the word " phthisis," which means " wasting away " or " decay," and was used by Hippocrates, accurately describes the morbid process in tuberculosis generally, as well as the constitutional effect on the patient in consumption. According to the most recent views, the presence and multiplication of the bacilli excite by irritation the growth of epithelioid cells from the normal fixed cells of the tissue affected, and so form the tubercle, which at first consists of a collection of these morbidly grown cells. In a typical tubercle there is usually a very large or " giant " cell in the centre, surrounded by smaller epithelioid cells, and outside these again a zone of leucocytes. The bacilli are scattered among the cells. In the earliest stages the tubercle is microscopic, but as several of them are formed close together they become visible to the naked eye and constitute the condition known as miliary tubercle, from their supposed resemblance to millet seeds. In the next stage the cells forming the tubercle undergo the degenerative change known as " caseation," which merely means that they assume in the mass an appearance something like cheese. In point of fact, they die. This degeneration is believed to be directly caused by a toxin produced by the bacilli. The further progress of the disease varies greatly, probably in accordance with the resisting power of the individual. In proportion as resistance is small and progress rapid the cheesy tubercles tend to soften and break down, forming abscesses that burst when superficial and leave ulcers, which in turn coalesce, causing extensive destruction of tissue. In proportion as progress is slow the breaking-down and " destructive process is replaced by one in which the formation of fibrous tissue is the chief feature. It may be regarded as Nature's method of defence and repair. In tuberculosis of the lungs, for instance, we have at one end of the scale acute phthisis or " galloping consumption," in which a large part or even the whole of a lung is a mass of caseous tubercle, or is honeycombed with large ragged cavities formed by the rapid destruction of lung tissue. At the other end we have patches or knots of fibrous tissue wholly replacing the original tubercles or enclosing what remains of them. Such old encapsuled tubercles may undergo calcareous degeneration. Between these extremes come conditions which partake of the nature of both in all degrees, and exhibit a mixture of the destructive and the healing processes in the shape of cavities surrounded by fibrous tissue. Such intermediate conditions are far more common than either extreme; they occur in ordinary chronic phthisis. The term " fibroid phthisis " is applied to cases in which the process is very chronic but extensive, so that considerable cavities are formed with much fibrous tissue, the contraction of which draws in and flattens the chest-wall. Tuberculosis commonly attacks one organ or part more than another, but it may take the form of an acute general fever, resembling typhoid in its clinical features. " Acute miliary tuberculosis " is a term generally used to indicate disseminated infection of some particular organ usually the lungs or one of the serous membranes in which the disease is so severe and rapid that the tubercles have not time to get beyond the miliary state before death occurs. Tuberculosis is exceedingly apt to spread from its original seat and to invade other organs. The confusing multiplicity of terms used in connexion with this disease is due to its innumerable variations, and to attempts to classify diseases according to their symptoms or anatomical appearances. Now that the cause is known, and it has become clear that different forms of disease are caused by variations in extent, acuteness and seat of attack, the whole subject has become greatly simplified, and many old terms might be dropped with advantage.

Tuberculosis in the Lower Animals. Most creatures, including worms and fishes, are experimentally susceptible to tuberculosis, and some contract it spontaneously. It may be called a disease of civilization. Domesticated animals are more susceptible than wild ones, and the latter are more liable in captivity than in the natural state. Captive monkeys, for instance, commonly die of it, and of birds the most susceptible are farmyard fowls, but it is practically unknown in animals in the wild state. In cattle coming chiefly from the plains (United States Bureau of Animal Industry Reports, 1900-1905) the number found diseased was only 0-134% in 28,000,000. Of the domesticated animals, horses and sheep are least, and cattle most, affected; pigs, dogs and cats occupy an intermediate position.

The percentage of tuberculous animals recorded at the slaughterhouses of Berlin in 1892-1893 was as follows: Cows and oxen, 15-1; swine, 1-55; calves, o-n; sheep, 0-004. Similar records at Copenhagen in 1890-1893 give the following result: Cows and oxen, 17-7; swine, 15-3; calves, 0-2; sheep, 0-0003. The order of the animals is the same, and it is confirmed by other slaughterhouse statistics; but the discrepancies between the figures indicate considerable variation in frequency, and only allow general conclusions to be drawn. A striking fact is the comparatively small amount of tubercle in calves. It shows, as Nocard has pointed out, that heredity cannot play an important part in the transmission of bovine tuberculosis. The infrequency of the disease in sheep is attributed to the open-air life they lead, and no doubt that is an important factor. The more animals and persons are herded together and breathe the same air in a confined and covered space, the more prevalent is tuberculosis among them. Stefansky found the disease in 5% of the rats caught in Odessa, and Lydia Rabinowitch obtained similar results in rats caught in Berlin. But there are evidently degrees of natural resistance also. Horses are more confined than cattle in the United Kingdom, yet they are far less affected; and on the other hand, cattle running free in the purest air may take the infection from others. Professor McEacharn of Montreal states that he has seen tuberculosis prevalent in ranch cattle, few of which were ever under a roof, ranging on the foothills of the Rocky Mountains in Montana. In cows and monkeys the lungs are chiefly affected; in horses and pigs the intestine and abdominal organs.

The relation between human and animal tuberculosis has been much debated. The bacillus in man very closely resembles that found in other mammalia, and they were considered identical until Koch threw doubt on this view at the British Congress on Tuberculosis in 1901. The British government thereupon appointed a royal commission to inquire into the relations of human and animal tuberculosis. The second interim report of the commission was issued in 1907, and the conclusions arrived at in it are: " That there seems to be no valid reason for doubting the opinion, never seriously doubted before 1901, that human and bovine bacilli belong to the same family. On this view the answer to the question, Can the bovine bacillus affect man? is obviously in the affirmative. The same answer must also be given to those who hold the theory that human and bovine tubercle bacilli are different in kind, since the ' bovine kind ' are readily to be found as the causal agents of many fatal cases of human tuberculosis." The commission also found that there is an essential unity not only in the nature of the morbid processes induced by -human and bovine tubercle bacilli, but also in the morphological characteristics exhibited by the tubercle bacilli which cause these processes. . The conclusions of the members of the Paris Congress on Tuberculosis, held in 1905, are: " That human tuberculosis can be transferred to the bovine animal, and that what is termed the bacillus of bovine origin can be discovered in the human subject, and that there is a possibility that they may be varieties of one species."

The distribution of tuberculosis is universal, and it is coincident with Distribution the existence of the human race in the habitable and regions of the globe. Its comparative absence in Mortality. t jj e Arctic regions seems more due to the sparsity of population than to climatic effect. Indeed, it has been shown that climate has much less effect in its prevalence than has been formerly thought to be the case, the conclusion of Hirsch being that " the mean level of the temperature has no significance for the frequency or rarity of phthisis in any locality." The nature of the occupations and the density of population in any given area tend to its increase or otherwise, and the comparative immunity enjoyed by uncivilized races is due to their open-air life and to the sanitary advantages derived from the comparatively frequent changes of the sites of their camps and villages. Segregation of these races in fixed areas has shown an increased incidence of tuberculosis, and when living under civilized conditions they fail to exhibit any natural immunity. Altitude has an apparent influence on the frequency of phthisis, the rarity of the disease at high altitudes in Switzerland having been demonstrated, and a like protective influence is enjoyed by certain elevated districts in Mexico, notwithstanding the insanitary conditions of the towns thereon. The protection afforded by the altitude is alleged to be due to the dryness of the atmosphere, its freedom from impurities and the increased solar radiation. While no race is exempt from tuberculosis, certain races afford a greater case incidence. E. Baldwin states that the mortality from consumption in recently immigrated races in the United States is much greater than in those of longer residence. It was found that among those whose mothers were of foreign birth the rate was in Russians 71-8, Germans 167, Scottish 172-5, French 187-7 an( l Irish 33Q-6, while in native-born Americans it was 1 1 2-8. The well-known susceptibility of the Irish has been attributed to the moisture of the climate, under-feeding, and the residual inferiority of a population drained by the emigration of a large number of able-bodied adults. That there is some added factor is shown by the fact that the above mortality of 339 in those having Irish mothers, in 1901, was greater by 31% than that of the Irish in Ireland at the same period. The Jews are said to show a relative immunity, but the matter requires further investigation. The factor which seemingly has the most constant influence on the mortality from tuberculosis is density of population. A high rate of mortality occurs in connexion with overcrowding and bad ventilation in cities, and it is proved that the death-rate from this disease is considerably lower in the country than in the towns. In addition, when we consider that it does not occur in epidemics or at certain seasons, but is constantly active, it will easily be seen that no other disease is so destructive to the human race. At the Tuberculosis Congress, held in Paris in 1905, it was stated by Kayserling that one-third of all deaths and one-half the sickness amongst adults in Germany was due to tuberculosis.

In 1908 the mortality from all forms of tuberculosis in England and Wales was, according to the registrar-general's returns, 56,080, less by 3455 than the average of the previous five years, being equal to 10-8% of the mortality from all causes, while in Ireland in 1909 14% of the total mortality was assigned to it.

The following table gives the comparative mortality from pulmonary tuberculosis for certain fixed years together with the estimated population of certain selected countries:

Estimated Population in Years.

Mortality from Pulmonary Tuberculosis.

1892.

I9OO.

1907.

1892.

1900.

1907.

England and Wales Ireland .... German Empire . France .... Norway .... Italy .... Holland .... Belgium .... Switzerland .

29,760,842 4,633,808 47.I 2 5,446 38,360,000 2,010,000 30,665,662 4,645,660 6,195-355 3,002,263 32,249,187 4,468,501 52,624,706 38,9OO,OOO 2,211,300 32,346,366 5-159,347 6,693,548 3,299,939 34,945-600 4,377,064 61,994,743 39,222,000 2,305,700 33,776,087 5,709,755 7,317,561 3-525,290 43,323 10,048 113,720 31,080 3,358 39,715* 8,906 10,491 5,785 42,987 10,076 108,827 34,357 4,249 41,733* 8,451 9,"7 6,692 39,839 8,828 97-555 40,304 4.656 41,968* 7-403 7,377 6,063 * In Italy the mortality given is for all forms of tuberculosis.

We thus see there is a general tendency to decrease in the deathrate, with the possible exception of France and Norway. In England the decrease has been most marked, having fallen from 3457 per million living in 1851-1860, or 15-6% of all deaths, to 1583 per million living, or a mortality of 10-8 % of the death-rate from all causes for all ages and sexes. Death-rate of Tuberculosis per million living in England and Wales, 1zz 860.

1870.

1880.

1890.

I9OO.

1908.

Males Females .... Both Sexes 3300 3300 3300 3300 3000 3150 2900 2500 2700 2700 2IOO 24OO 22OO I&OO 1900 1800 1350 1583 In English counties containing populations of 100,000 or over the highest rates were in 1908 London, 1806; Lancashire, 1848; Northumberland, 1947; Carnarvonshire, 2025; and Carmarthenshire, 2328 per million living. Of the fifteen counties in England and Wales with the highest tuberculosis mortalities, no fewer than seven are Welsh. Cardiganshire, with 2270 for both sexes, has a rate nearly double that of England.

According to the United States census of 1900, the death-rate from tuberculosis in the area chosen for registration which embraced ten registration states, namely, Connecticut, Maine, District of Columbia, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Rhode Island and Vermont, and 153 registration cities outside these states, was: .

Number of Deaths from Tuberculosis.

Death-rate per 100,000.

1890 1900 48,236 54-898 245-4 190-5 i by phthisis at ages under 5 years, more liable at the age of 5-20, and again less liable at subsequent ages." These observations, it must be noted, refer only to consumption. The comparative immunity of the very young does not extend to all forms of tuberculous disease. On the contrary, tuberculosis of the bowels and mesenteric glands (tabes mesenterica), tuberculous peritonitis and tuberculous meningitis are pre-eminently diseases of childhood. The tables at foot of page show in detail the relative incidence of pulmonary phthisis at different ages, and the steady diminution of the disease in England and Wales since 1850.

Occupation has a marked influence on the prevalence of pulmonary tuberculosis. The comparative mortality figures for vanous occupations are taken from the supplement to the registrar-general's 6sth annual Report, and show the incidence of pulmonary phthisis, agriculturists being taken at 100 for purposes of comparison. Occupied Males: England and Wales.

The returns of the mortality statistics of the United States for the year 1908 cover an area of 17 states, the district of Columbia and 74 registration cities, representing an aggregate population of 45,028,767, or 51-8 % of the total estimated population of the United States.

Mortality from Tuberculosis in the United States in given areas.

Annual Average, 1901-1905.

Tuberculosis (all forms) , 62,833- Pulmonary Phthisis, S5,25i- Number Tuberculosis fall forms) per 100,000 of the population, 103-2.

1904 1905 1906 1907 1908 66,797 65,352 75,512 176,650 78,289 58,763 56,770 65,341 66,374 67,376 201-6 193-6 184-2 183-6 173-9 In the United States tuberculosis of the lungs forms from 86 to 87 % of all cases. The death-rate, as we see, is steadily decreasing. It is, however, difficult to estimate the ravages of the disease in that country owing to the fact that rather less than half the United States is still unprovided with an adequate system of registration.

The following was the death-rate from tuberculosis (all forms) per 100,000 of the population of the chief cities of the United States during 1908:

Highest. Tin miner . Copper miner . Scissors maker File maker . General shopkeeper Brush maker . 816 574 533 387 387 325 Furrier 316 Printer 300 Chimney sweep . . . 284 Hatter . . 280 156 158 159 165 194 '97 Lowest.

Coal miner .... 89 Chemical manufacturer 98 Carpenter, joiner . . 150 Artist . . . Blacksmith . Worsted manufacturer Baker . . . Bricklayer . Cotton manufacturer .

Tailor 248 The high incidence in the first group will be seen chiefly to affect those occupations where there is dust (scissors and file makers and furriers). The high mortality amongst general shopkeepers can onjy be ascribed_ to continuous indoor occupation. Coal miners enjoy an unexplained immunity.

Dr Von Korosy has tabulated the result of seventeen years' observation in Budapest, which is an excessively tuberculous town. His figures include both males and females above fifteen years of age, and extend to 106,944 deaths. The field of observation is evidently very different from those which furnished the statistics already given. His results are: (i) Males printers 606, butlers 520, shoemakers 494, dyers 493, millers 492, joiners 485, tinkers and locksmiths 484, masons 467, labourers 433, tailors 418, bakers 398, drivers 370, servants 360, carpenters 339, officials 336, butchers 333, innkeepers 272, merchants 253, lawyers 205, physicians 1 1 8, capitalists 106; (2) Females servants 353, day labourers (? char-women) 333, washerwomen 314, gardeners 269, capitalists 42. The inmates of lunatic asylums, who are classed among the New Orleans 298-3 Sacramento, California .... 294-3 Washington 264-0 Baltimore 249-9 Jersey City 241-1 New York 234-4 Philadelphia 234-1 Saratoga Springs, New York . . 232-2 Indianapolis 222-6 Boston, Massachusetts .... 219-1 St Louis 188-3 Chicago 180-7 Kansas City 172-9 Cleveland, Ohio 142-4 Pittsburg, Pennsylvania . . . 139-2 Detroit 122-5 St Paul, Minnesota . . . .111-8 The returns in the United States show a high rate of mortality from tuberculosis amongst the coloured population, the negro being particularly susceptible to pulmonary _ phthisis; the death-rate from this cause is nearly double that amongst whites.

Age and Sex. The most complete information under this heading is derived from the English records. "In both sexes," says Dr Tatham, " the real liability to phthisis begins somewhere between the fifteenth and the twentieth year. Among males it attains its maximum at age 45-55, when it reaches 3173 per million living. Among females it attains its maximum (2096) at age 35-45. In both sexes the rate rapidly declines after _the attainment of its maximum. Practically the incidence of pulmonary phthisis is upon the ages from 15 to 75. years, ^very old people and young children being comparatively exempt. According to recent experience, females seem to be rather less liable than males to death ENGLAND AND WALES Tuberculous Phthisis. Mortality in several Periods, 1851-1899.

Annual Rate per Million Living.

MALES.

AGES.

Period.

Under Ages.

5 Years.

25 1zz 5- 1851-1860 2579 1329 1zz 63 2399 4052 4031 4004 3830 3231 2389 1861-1870 2467 1zz 31 1zz 190 3883 4094 4166 3861 3297 2024 1871-1880 2209 1zz 40 1zz 675 3092 3699 4120 3860 3195 1924 1881-1885 1927 1zz 74 1zz 381 2467 3246 3726 3567 2937 1800 1886-1890 1781 1zz 34 1zz 212 2222 2842 3436 3446 2904 1845 1891-1895 1634 1zz 97 1zz 075 2O26 2548 3268 3205 2686 1572 1896-1899 1521 1zz 40 1zz 08 1841 2341 3110 3173 2627 1530 1900-1904 1zz 66 1zz 82 1zz 643 2147 2811 3130 2560 1309 1903-1907 1385 1zz 38 1zz 43 1472 2022 2573 2945 2498 1316 1908 1310 1zz 34 1zz 76 I8 5 8 2114 1964 2OOO 1830 1061 AGES.

Period.

Under Ages.

5 Years.

25 1zz 5- 1851-1860 2774 1281 1zz 293 3516 4288 4575 4178 3121 2383 1635 1861-1870 2483 1zz 77 1045 1zz 967 4378 3900 2850 2065 1239 1871-1880 2028 1zz 75 1zz 397 3140 3543 3401 2464 1777 1093 1881-1885 1738 1zz 50 1zz 006 2596 3070 2927 2197 1541 1886-1890 1497 1zz 07 1zz 626 2075 2552 2563 1936 1490 1891-1895 1303 1zz 60 1zz 428 1740 2155 2305 1742 1294 1896-1899 1141 1zz 01 1zz 165 1547 1862 2096 1597 1242 1900-1904 1042 1zz 03 IOO2 1274 1593 1807 1481 1136 1903-1907 1zz 08 1zz 91 "94 1488 1643 1382 1075 1zz 908 1zz 29 1zz 41 1270 1438 1761 1407 1156 1zz 54 Heredity.

" unoccupied," suffer excessively from tubercle. According to Dr Mott, pathologist to the London County Council, tuberculous lesions are found in more than one-third of the bodies of inmates examined post mortem. The majority contract the disease in the asylums.

Medical opinion has undergone a great change with regard to the influence of heredity. The frequent occurrence of consumption among members of the same family used to be explained by assuming the existence of a tuberculous "diathesis" or inherent liability to consumption which " ran in families " and was handed down from one generation to another. As the real nature of the disease was not understood, the inherited diathesis was regarded as a sort of latent or potential consumption which might develop at any time and could hardly be avoided. The children of consumptive parents had the " seeds " of the disease in them, and were thought to be doomed with more or less certainty. Great importance was therefore attached to heredity as a factor in the incidence of tuberculosis. The discovery that it is caused by a specific parasitic infection placed the question in a different light, and led to a more careful examination of the facts, which has resulted in a general and increasing tendency to minimize or deny the influence of heredity. At the Berlin Congress on Tuberculosis in 1899 Virchow pronounced his disbelief in the theory on pathological grounds. " I dispute this heredity absolutely," he said. " For a course of years I have been pointing out that if we examine the bodies of infants newly born, who have had no life apart from the mother, we find no tuberculosis in them. I am convinced that what looked like tuberculosis in the newly born was none of it tuberculosis. In my opinion there is no authenticated case of tubercle having been found in a dissected newly-born infant." Observations on animals similarly tend to disprove the existence of congenital tuberculosis (Nocard). The theory that the germs may remain latent in the offspring of tuberculous parents (Baumgarten) is unsupported by evidence. The occurrence of disease in such offspring is ascribed to infection by the parents, and this view is confirmed by the fact that the incidence in consumptive families is greater on female children, who are more constantly exposed to home infection, than on the male (Squire). The statistical evidence, so far as it goes, points in the same direction. It is even denied that the children of consumptives are specially predisposed.

Recognition of the communicability of tuberculosis has directed attention to the influence of conditions in which people live massed together in close proximity. The preDeasityot valence of the disease in large centres of populaandove* ^ on nas already been noted, and the influence of crowding, aggregation is no doubt considerable; but it does not always hold good. The distribution in England and Wales does not correspond with density of population, and some purely rural districts have a very high mortality. Broadly, however, the rural counties have a low mortality, and those containing large urban populations a high one. In France in the department of the Oise, in purely industrial villages, the mortality from pulmonary phthisis is from 56 to 61 per 10,000; in a village in which part of the population worked in the fields and part in factories the mortality was 46 per 10,000; and in purely agricultural villages it ranged from o to 10 per 10,000.

The following table is taken from the Supplement to the RegistrarGeneral's 65th Report for England and Wales :

diseases in relation to overcrowding, the same authority found that " while associated with overcrowding is a tendency of the population to die from disease generally, this tendency is especially manifested in the case of phthisis, and is not manifested in the case of every disease."

Other Conditions. Poverty, insufficient food and insanitary dwellings are always more or less associated with overcrowding, and it is difficult to distinguish the relative influence of these factors. An. analysis of 553 deaths Ji Edinburgh according to rentals in 1899 gave these results: under 10, 230; from 10 to 20, 190; above 20, 106 (Littlejohn) ; but the corresponding population is not stated. An investigation of selected houses in Manchester gave some interesting results (Coates). The houses were divided into three classes: (i) infected and dirty; (2) infected but clean; (3) dirty but not infected; infected meaning occupied by a tuberculous person. Dust was taken from all parts of the rooms and submitted to bacteriological tests. The conclusions may be summarized thus: The effects of overcrowding were not apparent; a large cubic space was found to be of little avail if the ventilation was bad; the beneficial effects of light and fresh air were markedly shown even in the dirtiest houses; ordinary cleanliness was found not sufficient to prevent accumulation of infectious material in rooms occupied by a consumptive; no tuberculous dust was found in dirty houses in which there was no consumption. The upshot is to emphasize the importance of light and air, and to minimize that of mere dirt. This is quite in keeping with earlier investigations, and particularly those of Dr Tatham on back- toback houses. Darkness and stuffiness are the friends of the tubercle bacillus.

So much has the question of cleanliness, and of housing in a sanitary district, to do with the prevalence of the disease, that the following table taken from the Report of the Registrar-General for Ireland for the year 1909 shows the marked class incidence in all forms of tuberculosis.

Distribution of Tuberculosis Mortality by Classes in Ireland, ipop.

All forms of Tuberculosis.

Pulmonary Phthisis.

Other forms of Tuberculosis.

Professional and independent class Middle class, civil service and smaller officials .... Large traders, business managers Clerks I-4I 1-82 i-59 2-Q2 0-64 1-30 I-O4 2>77 , '77 0-52 o-55 O'CQ ' Householders in 2nd-class localities Artisans Petty shopkeepers and other traders Domestic servants .... Coach and car drivers, and vanmen Hawkers, porters and labourers 2-52 2-94 3-85 i-3i 4-24 4-83 1-85 2-23 3-00 1-04 3-06 2-88 O-67 0-71 0-85 0-27 1-18 1-95 In relation to the last two classes the effect of exposure and also of alcoholic excess must be added to overcrowding and privation. The low rate noticeable for domestic servants must be ascribed to the better food and housing they enjoy while in situations. In Hamburg the mortality was 10-7 per 10,000 in those whose income rose above 3500 marks, 39-3 where the income was 900 to 1200 marks, and 60 per 10,000 where the income fell below that figure.

It is now generally accepted that tubercle bacilli may enter the body by various paths. At the International Congress on Tuberculosis held in Vienna in 1907 Weichselbaum summarized the channels of infection in pulmonary tuberculosis as follows:

All occupied Males.

Occupied Males (London).

Occupied Males (industrial districts).

Occupied Males (agricultural districts).

All Causes .... Tuberculous Phthisis.

1900-1902.

1890-1892.

1900-1902.

1890-1892.

1900-1902.

1890-1892.

1900-1902.

1890-1892.

IOO IOO 122 119 156 183 1zz 56 147 72 71 86 90 It will be noted that the rate in the agricultural districts is low compared to the industrial districts or purely urban district chosen. There is obviously a close relation between density of population and the prevalence of phthisis. Comparing phthisis with other (i) By inhalation directly into the bronchioles and pulmonary alveoli, or by way of the bronchial glands through the blood and lymph channels into the lung. (2) Through the mucous membrane of the nose, mouth or tonsils into the neighbouring lymphatic glands, and thence through the blood or lymph into the lungs. (3) By ingestion of tubercle bacilli infection. into the lower P art f the gastro-intestinal tract in the food; thence the bacilli may pass through the lining membrane, infect the neighbouring glands and pass by the blood or lymph stream to the lungs. (4) By penetration of other mucous membranes (such as the conjunctival or urogenital) or through the skin. (5) Possible, though very rare, placental infection.

Tubercle bacilli may not produce any anatomical lesion at the point of entrance, or they may remain latent for a very long time; and it has been experimentally proved that they may pass through mucous membranes and leave no trace of their progress. As reported to the Royal Commission, the introduction of bacilli into the alimentary canal is not necessarily followed by the development of tuberculosis. The writings of Von Behring have led to renewed attention being paid to intestinal infection, particularly through the milk supply. Von Behring suggests that the bacillus itself may become modified in the human body.

Measures for the prevention of tuberculosis may be divided into two classes: (i) general; (2) special. Great attention _ . has been paid to the latter since the infectious "'nature of the disease was established. The former include all means by which the conditions of life are improved among the mass of the people. The most important of these are probably housing and food supplyj The reduction of the disease recorded in England is attributed to the great changes which have gradually taken place in such conditions since, say, 1850. Wages have been raised, food cheapened, housing improved, protection afforded in dangerous trades, air spaces provided, locomotion increased, the ground and the atmosphere have been cleaned and dried by sanitary means. In addition to these general measures is the provision of consumption hospitals, which act by segregating a certain amount of disease. Yet all these things, beneficial as they may be, do not wholly account for the reduction, for, if the records can be trusted, it was in progress before they had made any way or had even been begun. This observation, coupled with the apparently general tendency to diminution among civilized races, suggests the operation of some Jarger agency. The theory of acquired resistance, which has been already mentioned, would explain the diminution; and it is also in keeping with other facts, such as the great susceptibility of savage races, which have not been long exposed to tuberculosis, and the results of laboratory experiments in artificial immunity. The point is of great importance, and deserves careful attention; for if the theory be correct, the special measures for preventing tuberculosis, which are occupying so much attention, may eventually have unexpected results. Their general aim is the avoidance of infection, and they include (i) the provision of special institutions hospitals, sanatoria and dispensaries; (2) the prevention ' of spitting; (3) the notification of consumption; (4) the administrative control of tuberculosis in animals; (5) the dissemination of popular knowledge concerning the nature of the disease.

The greatest stress is laid upon the prevention of spitting, because the germs are contained in the sputum of consumptive persons, and are scattered broadcast by expectoration. The sputum quickly dries, and the bacilli are blown about with the dust. There is no question that infection is so conveyed. The Manchester scientific experiments, mentioned above, are only one series out of many which prove the infectivity of dust in the proximity of consumptive persons, and they are confirmed by actual experience. Several cases are recorded of healthy persons having contracted the disease after occupying rooms in which consumptive persons had previously lived. It is a legitimate inference that spitting in public is an important means of disseminating tuberculosis, though it may be noticed that international prevalence by no means corresponds with this disgusting practice, which is a perfect curse in Great Britain, and far more common both there and in the United States than on the continent of Europe. Prohibition of spitting under a statutory penalty is attended with certain difficulties, as it is obviously impossible to make any distinction between tuberculous and other persons; but it has been applied in New York and elsewhere in America, and some local authorities in Great Britain have adopted by-laws to check the practice. Another means of controlling dangerous sputa is more practicable, and probably more effective, namely, the use of pocket spittoons by consumptive persons. Convenient patterns are available, and their use should always be insisted on, both in public and in private. The most effective way of destroying the sputa is by burning. For this purpose spittoons of papier mache and of turf have been successfully used in the Vienna hospitals (Schrotter). When glass spittoons are used the contents can be sterilized by disinfectants and passed down the drain.

Notification is of great service as an aid to practical measures of prevention. It has been applied to that purpose with good results in several cities and states in America, and in some towns in Great Britain. New York has made the most systematic use of it. Voluntary notification was adopted there in 1894, and in 1897 it was made compulsory. The measures linked with it are the sanitary supervision of infected houses, the education of the people and the provision of hospitals. In England, Manchester has led the way. Voluntary notification was adopted there in 1899: it was at first limited to public institutions, but in 1900 private practitioners were invited to notify their cases, and they heartily responded. In Sheffield notification was made compulsory by a local act in 1904 for a limited period, and was found so valuable that the period was extended in 1910. The objects aimed at are to visit homes and instruct the household, to arrange and provide disinfection, to obtain information bearing on the modes of infection, to secure bacteriological examination of sputum, and to collect information to serve as a basis of hospital provision. Disinfection is carried out by stripping off paper, previously soaked with a solution of chlorinated firne (\\ oz. to the gallon), and washing the bare walls, ceiling, floor and everything washable with the same solution. This is found effective even in very dirty houses. In clean ones, where the patients have not been in the habit of spitting about the rooms, it is sufficient to rub the walls with bread-crumb and wash the rest with soap and water. Clothing, bedding, etc., are disinfected by steam. The advantages of these sanitary measures are obvious. Notification is no less important as a step towards the most advantageous use of hospitals and sanatoria by enabling a proper selection of patients to be made. It is compulsory throughout Norway, and is being adopted elsewhere, chiefly in the voluntary form. In 1908 the Prevention of Tuberculosis (Ireland) Act was passed, which conferred on local authorities the right to make notification compulsory in their districts, and provided that certain sections of the Public Health (Ireland) Act 1878 and the Infectious Diseases Prevention Act 1890 should apply to tuberculosis. By this act also the county councils were enabled to establish hospitals and dispensaries for the treatment of tuberculosis and were empowered to borrow money or levy a poor rate for the erection of sanatoria for the treatment of persons from their respective counties suffering from the disease.

The prevalence of tuberculosis in cattle is of importance from the point of view of prevention of the probability that abdominal tuberculosis, which is a very fatal form of the disease in young children, and has not diminished in prevalence like other forms, is caused by the ingestion of tuberculous milk. Whether it be so or not, it is obviously desirable that both meat and milk should not be tuberculous, if it can be prevented without undue interference with commercial interests. Preventive measures may be divided into two classes. They may deal merely with the sale of meat and milk, or they may aim at the suppression of bovine tuberculosis altogether. The former is a comparatively easy matter, and may be summed up in the words " efficient inspection." The latter is probably impracticable. If practicable, it would be excessively costly, for in many herds one half the animals or even more are believed to be tuberculous, though not necessarily the sources of tuberculous food. Unless the danger is proved to be very much greater than there is any reason to suppose, " stamping out " may be put aside. Efficient inspection involves the administrative control of slaughterhouses, cowsheds and dairies. The powers and regulations under this head vary much in different countries; but it would be useless to discuss them at length until the scientific question is settled, for if the reality of the danger remains doubtful, oppressive restrictions, such as the compulsory slaughter of tuberculous cows, will not have the support of public opinion. Whatever measures may be taken for the public protection, individuals can readily protect themselves from the most serious danger by boiling milk; and unless the source is .beyond suspicion, parents are recommended, in the present state of knowledge, so to treat the milk given to young children.

A great deal has been done in most countries for the dissemination of popular knowledge by forming societies, holding conferences and meetings, issuing cheap literature, and so forth. It is an important item in the general campaign against tuberculosis, because popular intelligence and support are the most powerful levers for setting all other forces in motion. In Ireland, where an attempt had been made to deal with the question by arousing the interest of all classes, tuberculosis exhibitions have been held in nearly every county, together with lectures and demonstrations organized by the Women's National Health Association; and an organized attempt was made in the autumn of 1910 in England, by a great educational campaign, to compel the public to realize the nature of the disease and the proper precautions against it.

The improved outlook in regard to the arrest or so-called " cure " of tuberculosis is mainly derived from the improved Diagnosis methods of diagnosis, thus enabling treatment to ""I be undertaken at an earlier and therefore more Treatment. f avoura bl e stage of the disease. The physical signs in early stages of the lung . affection are often vague and inconclusive. A means of diagnosis has therefore been sought in the use of tuberculin. The methods are three: (i) The subcutaneous injection method of Koch; (2) the cutaneous method of Von Pirquet; (3) the conjunctiva! method of WolffEisner and Calmette. The first method depended on the reaction occurring after an injection of " old tuberculin." It is unsuitable in febrile conditions, and has now been relegated to the treatment of cattle, where it has proved invaluable. In Von Pirquet's method a drop of old tuberculin diluted with sodium chloride is placed on a spot which has been locally scarified. The presence of tuberculosis is demonstrated by a local reaction in which a hyperaemic papule forms, surrounded by a bright red zone. Reaction occurs in tuberculosis of the bones of joints and skin. Von Pirquet in 1000 cases obtained a reaction in 88% of the tuberculous, and 10% of those clinically non-tuberculous. In the latter there may have been latent cases of tuberculosis. In the conjunctiva! or opthalmo-reaction of Calmette and Wolff-Eisner the instillation of a drop of a dilute solution of tuberculin into the conjunctiva is followed in the tuberculous subject by conjunctivitis. The reaction generally appears in from 3 to 12 hours, but may be delayed to 48. In a series of cases observed by Audeoud a positive reaction was obtained in 95% of 261 obviously tuberculous cases and in 8-3 % of 303 cases which presented no clinical symptoms. Very advanced cases fail to react to any of these tests, as do general miliary tuberculosis and tuberculous meningitis. As well as the three methods mentioned above the occurrence of a " negative phase " in the phagocytic power of the leucocytes following an injection of Koch's tuberculin T.R. may be said to be diagnostic of tuberculosis. Another valuable aid in diagnosis is that of the X-rays. By their help a pulmonary lesion may be demonstrated long before the physical signs can be obtained by ordinary examination.

To discuss at all fully the treatment of the various forms of tuberculosis or even of consumption alone would be quite beyond the scope of this article. It must suffice to mention the more recent points. The open-air treatment of consumption has naturally attracted much attention. Neither the curability of this disease nor the advantages of fresh air are new things. Nature's method of spontaneous healing, explained above, has long been recognized and understood. There are, indeed, few diseases involving definite lesions which exhibit a more marked tendency to spontaneous arrest. Every case, except the most acute, bears signs of Nature's effort in this direction; and complete success is not at all uncommon, even under the ordinary conditions of life. Perhaps it was not always so: the ominous character popularly attributed to consumption may once have been justified, and the power of resistance, as we see it now, may be the result of acquired immunity or of the gradual elimination of the susceptible. However this may be, the natural tendency to cure is undoubtedly much assisted by the modern system of treatment, which makes pure air its first consideration. The principle was known to Sydenham, who observed the benefit derived by consumptives from horse exercise in the open air; and about 1830 George Boddington proposed the regular treatment of patients on the lines now generally recognized. The method has been most systematically developed in Germany by the provision of special sanatoria, where patients can virtually live in the open air. The example has been followed in other countries to a certain extent, and a good many of these establishments have been provided in Great Britain and elsewhere; but they are, for the most part, of a private character for the reception of paying patients. Germany has extended these advantages to the working classes on a large scale. This has been accomplished by the united efforts of friendly and philanthropic societies, local authorities, and the state; but the most striking feature is the part played by the state insurance institutes, which are the outcome of the acts of 1889 and 1899, providing for the compulsory insurance of workpeople against sickness and old age. The sanatoria have been erected as a matter of business, in order to keep insured members off the pension list, and they are supported by the sick clubs affiliated to the institutes. They number forty-five, and can give three months' treatment to 20,000 patients in the year. The clinical and economic results are said to be very encouraging. In about 70% of the cases the disease has been so far arrested as to enable the patients to return to work.

In England, where more than 14 millions of the population belong to friendly societies, it is estimated that the sick pay of consumptive members costs three times as much as the average sick pay to members dying of other causes. An effort has been made by the National Association for the Establishment and Maintenance of Sanatoria for Workers Suffering from Tuberculosis to establish such sanatoria, together with training for suitable work during convalescence, the gradual resumption of wage-earning being resumed while in touch with the medical authorities.

The important features of the sanatorium treatment are life in the open air, independently of weather, in a healthy situation, rest and abundance of food. The last has been carried to rather extravagant lengths in some institutions, where the patients are stuffed with food whether they want it or not. The sanatorium movement on the German model is rapidly extending in all countries. For those who are able to do so advantage may be taken of the combined sanatorium and Sun treatment. In certain high altitudes in Switzerland, which are favoured by a large amount of sunshine and a small percentage of moisture, much benefit has been derived from the exposure of the unclothed body to the sun's rays. The power of the Sun in high altitudes is so great that the treatment can be continued even when the snow is on the ground. Not only is the sun-treatment applicable to pulmonary tuberculosis, but also to the tuberculosis of joints, even in advanced cases. The treatment has to a great extent replaced surgical procedure in tuberculosis of joints, but it requires to be persevered in over a considerable period of time. It should be remembered that the benefits of fresh air are not confined to sanatoria. If the superstitious dread of the outer air, particularly at night, could be abolished in ordinary life, more would be done for public health than by the most costly devices for eluding microbes. Not only consumption, but the other respiratory diseases, which are equally destructive, are chiefly fomented by the universal practice of breathing vitiated air in stuffy and overheated rooms. The cases most suitable for the treatment are those in an early stage. Other special institutions for dealing with consumption are hospitals, in which England is far in advance of other countries, and dispensaries; the latter find much favour in France and Belgium.

In Great Britain the pioneer work as regards the establishment of tuberculosis dispensaries was the establishment of the Victoria Dispensary for Consumption in Edinburgh in 1887, where the procedure is similar to that in Dr Calmette's dispensaries in France. In connexion with the dispensary home visits are made, patients suitable to sanatoria selected, advanced cases drafted to hospitals, bacteriological examinations made, cases notified under the voluntary system, and the families of patients instructed. There is an urgent need for the multiplication of such dispensaries throughout the United Kingdom. The recent act providing for the medical inspection of schools has done much to sort out cases of tuberculosis occurring in children, and to provide them with suitable treatment and prevent them from becoming foci for the dissemination of the disease. In Germany special open-air schools, termed forestschools, are provided for children suffering from the disease, and an effort is being made in England to provide similar schools.

Of specific remedies it must suffice to say that a great many substances have been tried, chiefly by injection and inhalation, and good results have been claimed for some of them. The most noteworthy is the treatment by tuberculin, first introduced by Koch in 1890, which, having sunk into use as a diagnostic reagent for cattle, received a new lease of life owing to the valuable work done by Sir Almroth Wright on opsonins. The tuberculins most in use are Koch's " old " tuberculin T.O., consisting of a glycerin broth culture of the tubercle bacilli, and Koch's T.R. tuberculin, consisting of a saline solution of the triturated dead tubercle bacilli which has been centrifuged. This latter is much in use, the dosage being carefully checked by the estimation of the tuberculo-opsonic index. The injections are usually unsuitable ^o very advanced cases. Marmorek's serum, the serum of horses into which the filtered young cultures of tubercle bacilli have been injected, and in which a tuberculo-toxin has been set free, has proved very successful. Behring's Tulase is a tuberculin preparation formed by a process of treating tubercle bacilli with chloral, and Bereneck's tuberculin consists of a filtered bouillon culture treated with orthophosphoric acid. The variety of cases to which these treatments are suitable can only be estimated from a careful consideration of each on its own merits.

In the treatment of tuberculous lesions, the surgeon also plays his part. Tuberculosis is specially prone to attack the spongy bone-tissue, joints, skin (lupus) and lymphatic glands especially those of the neck. Recognizing the infective nature of the disease, and knowing that from one focus the germs may be taken by the blood-stream to other parts of the body, and so cause a general tuberculosis, the surgeon is anxious, by removing the primary lesion, to cut short the disease and promote immediate and permanent convalescence. Thus, in the early stage of tuberculous disease of the glands of the neck, for instance, these measures may render excellent service, but when the disease has got a firm hold, nothing short of removal of the glands by surgical operation is likely to be of any avail. The results of this modern treatment of tuberculous disease of the skin and of the lymphatic glands has been highly gratifying, for not only has the infected tissue been completely removed, but the resulting scars have been far less noticeable than they would have been had less radical measures been employed. One rarely sees now a network of scars down the neck of a child, showing how a chain of tuberculous glands had been allowed to work out their own cure. A few years ago, however, such conditions were by no means unusual.

BIBLIOGRAPHY. " Tuberculosis," in Allbutt and Rotteston's System of Medicine (1909); A. Ransome, Milroy Lectures; " Tuberculosis," in Osier's Modern Medicine (1907); Second Interim Report of the Royal Commission on Tuberculosis (1907) ; Report, by C. Theodore Williams and H. Timbre!! Bulstrode, of the International Congress on Tuberculosis held at Paris in 1905; Alexander Foulerton, Milroy Lectures (1910); Sir Thomas Oliver, Diseases of Occupation; Arthur Newsholme, The Prevention of Tuberculosis (1908) ; Douglas Powell, " Lecture on the Prevention of Consumption," Journ. San. Inst. (Aug. 1904) ; Calmette and Gudrin, " Origine intestinale de la tuberculose pulmonaire," Annales de I'institut Pasteur, vol. xix. No.io; D. Muller, " Milk as a source of infection in Tuberculosis," Journ. Compar. Path, and Therapeutics, vol. xix. (H. L. H.)

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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