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TUBERCULOSIS

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Originally appearing in Volume V27, Page 356 of the 1911 Encyclopedia Britannica.
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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 mesenteries." 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, 19oo–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 slaughter-houses of Berlin in 1892–1893 was as follows: Cows and oxen, 15.1; swine, 1 • J 5, calves, o.11 ; sheep, 0.004. Similar records at Copenhagen in 1890-1893 give the following result: Cows and oxen, 17.7; swine, 15.3; calves, o•2; sheep, 0.0003. The order of the animals is the same, and it is confirmed by other slaughter-house 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 esser•tial 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 * In Italy the mortality given is for all forms of tuberculosis. Distribution the existence of the human race in the habitable We thus see there is a general tendency to decrease in the death- and regions of the globe. Its comparative absence in rate, with the possible exception of France and Norway. In England Mortality. the Arctic regions seems more due to the s arsit the decrease has been most or marked 15. ,o having fallen from 3457 per P y million living in 1851-186o, or 15.6 /o of all deaths, to 1583 per. of population than to climatic effect. Indeed, it has been million living, or a mortality of Io•8 % of the death-rate from all shown that climate has much less effect in its prevalence causes for all ages and sexes. England and Wales Ireland German Empire . France Norway Italy Holland Belgium Switzerland 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 and Irish 339.6, while in native-born Americans it was II2.8. 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 ,o•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. 1892. 29,760,842 4,633,808 47,125,446 38,360,000 2,010,000 30,665,662 4,645,660 6,195,355 3,002,263 1900. 32,249,187 4,468,501 52,624,706 38,900,000 2,211,300 32,346,366 5,159,347 6,693,548 3,299,939 1907. 34,945,600 4,377,o64 61,994,743 39,222,000 2,305,700 33,776,087 5,709,755 7,317,561 3,525,290 Mortality from Pulmonary Tuberculosis. 1892. 43,323 10,048 113,720 31,080 3,358 39,715* 8,906 10,491 5,785 1900. 42,987 10,076 108,827 34,357 4,249 41,733* 1907. 39,839 8,828 97,555 40,304 4,656 41,968* than has been formerly thought to be the case, the con- Death-rate of Tuberculosis per million living in England and Wales. elusion of Hirsch being that " the mean level of the tem- perature 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 8,451 9,117 6,692 186o. 187o. 1880. 189o. 1900. 1908. Males . . . 3300 3300 2900 2700 2200 1800 Females . . . 3300 3000 2500 2100 1600 1350 Both Sexes . . . 3300 3150 2700 2400 1900 1583 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 1H .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 in-formation 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 maxi-mum 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. Ac-cording to recent experience, females seem to be rather less liable than males to death TUBERCULOSIS I by phthisis at ages under 5 years, more liable at the age of 5-2o, 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 various occupations are taken from the supplement to the registrar-general's 65th annual Report, and show the incidence of pulmonary phthisis, agriculturists being taken at 100 for purposes of comparison. Occupied Males: England and Wales. Highest. Lowest. Tin miner 816 Coal miner . . . . 89 Copper miner 574 Chemical manufacturer 98 Scissors maker 533 Carpenter, joiner . 15o File maker 387 Artist 156 General shopkeeper 387 Blacksmith. . 158 Brush maker 325 Worsted manufacturer 159 Furrier 316 Baker 165 Printer 300 Bricklayer . . 194 Chimney sweep 284 Cotton manufacturer . 197 Hatter 28o 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 only 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 6o6, 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 36o, carpenters 339 officials 336, butchers 333; innkeepers 272, merchants 253, lawyers 205, physicians i18, 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
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