only note of 46 cases, and half of these were but of doubtful nature. Some few others are to be associated with phthisis, but as a substantive ailment we might have supposed it to be more common than it is." And Professor Gairdner, in his Lectures to Practitioners, draws attention to the fact that as pathological descriptions can deal with fatal cases only, a far too grave prognosis is arrived at in case of tabes, and that consequently many cases of tubercular disease, not only of the mesenteric glands, but also of the peritoneum, recover, only the more grave cases succumbing. It is evident from all this that tubercular conditions of the abdomen are much more common than can be inferred even from the figures above quoted, where only one-fifth of the real number are stated in the diagnosis charts to be suffering from abdominal tubercle. That there is a great tendency towards calcification and cicatrisation, especially where the tissues have a high resistant power, is well known to all pathologists, who constantly find cicatrices which are to be recognised as of tubercular origin (by the presence of small caseous or calcareous nodules, etc.), in which, however, the tubercle has become quiescent. These are the result of local tubercular changes, the localisation being due to the activity of the tissues.

(340) Probability of a Person Dying from Consumption. The late Dr. Farr from his life table calculated that 114,417 out of 1,000,000 children born would die of phthisis; at some or other period of their lives these might therefore be considered predisposed, or in other words they had less resistant power than other people. He then constructed a hypothetical life table of the class dying or to die of consumption, by picking out the survivors of the 114,417 at any age and putting them into a class apart. Such a table illustrates well the effect of age, e.g. :—

NUMBERS TO DIE OF CONSUMPTION AT AND AFTER EACH AGE OUT OF

(341) Influence of Occupation on Tubercle Infection.

Out-door occupations are less liable to tubercular maladies than in-door; a rural population is therefore less liable than an urban population. Those who are well housed and have ample cubic space are less liable than those living in the reverse conditions. The spread of tuberculosis in this respect strictly follows the law governing the spread of zymotic diseases generally. The oneroomed population of towns have a much higher mortality than those who can afford more than one room. Two causes tend to produce this result-the one is the low state of health breathing an impure atmosphere produces, and hence a less resisting power; the other is that the nearer the infected and the healthy are, the more prone is infection to be conveyed.

Dusty trades or occupations are especially liable to produce tubercular lung disease. C. Lombard (Recherches Anatomiques sur l'Emphysème pulmonaire) found the order of fatality to be (1) mineral dust; (2) animal; (3) vegetable. In 1,000 deaths from consumption of adults he found they could be classed according to their occupations as follows:

Occupations with mineral and vegetable emanations
Occupations with various dusts

Sedentary life

Workshop

.

Hot and dry air

Stooping posture

Sudden movements of the arms

Muscular exercise and active life

Exercise of the voice

Living in open air.

Animal emanations

Occupations in which watery vapour was breathed

176

145

140

138

127

122

116

89

75

73

60
53

This result is conformable to the micro-parasitic theory of tuberculosis. The researches of Greenleaf Tucker1 and others have clearly proved that the number of bacteria in the atmosphere of a room or place is dependent upon the greater or less amount of dust. In a quiet room, such for example as a hospital ward early in the morning, before any dusting, sweeping, or bed-making has been done, the bacteria are very small in numbers because they have settled down with the dust on the floor, the walls, and 1 Massachusetts State Board of Health Report, 1888.

G G

other objects; the bacteria attain their maximum number when there is the maximum amount of dust in the air. It is therefore no wonder that a disease like tuberculosis, so widespread and against which no precautions are taken, infects the dust of workshops and living rooms, and the bacilli, dust-borne, are breathed; nor is it a matter of surprise that metallic dust-that is, dust having sharp angles and spicule-should be more likely to wound the mucous epithelium and open a door as it were for the bacilli to enter, while the softer vegetable fibre has not so great an effect.

(342) Influence of Soil.

Drs. Bowditch and Buchanan, working independently, successfully established the fact that there is a relation between dampness of soil and tubercular affections. It is therefore probable that dampness of a house is also a predisposing cause, although the area in which the particular house stands may be dry. Sir John Simon and others have shown that the draining of soils diminish the death-rate from consumption. Dr. Andrews, of the Chicago Medical College, has studied the geographical distribution of consumption in the States, and has shown that there it is most abundant near the sea and diminishes as we recede from it. At equal distances from the sea it prevails at the north and diminishes towards the south. For example, beginning at Massachusetts and going westward, the proportion of deaths from consumption to deaths from all causes regularly diminishes as we recede from the Atlantic. Thus deaths from Massachusetts, 25 per cent.; New York, 20 per cent.; Ohio, 16 per cent.; Indiana, 14 per cent.; Illinois, 11 per cent.; Missouri, 9 per cent.; Kansas, 8 per cent.; Colorado, 8 per cent.; Utah, 6 per cent.; and then in California it increases again to 14 per cent. on account, according to Andrews, of the proximity of the Pacific Ocean. A similar decrease is observed in going from north to south-viz., Michigan, 16 per cent.; Indiana, 14 per cent.; Tennessee, 12 per cent.; Alabama, 6 per cent.

Hence tubercular disease seems to follow closely the moisture and temperature of localities. Massachusetts is ten times as fatal to consumptives as Georgia, and Minnesota is twice as fatal. as Georgia. The combinations of damp soil, an atmosphere laden

with moisture, and variable weather, are the most favourable, and the reverse of these the least favourable, for the dissemination of the malady.

(343) Influence of Season on Tubercular Fatality.

This has been worked out in Buchan and Mitchell's research.1 It would of course be more interesting to know at what season of the year the tubercular process commenced than when it terminated, but this is not possible until tuberculosis in all its forms is "notified" under the Infectious Diseases Notification Act.

Buchan and Mitchell have shown that the mortality from tabes follows very closely the temperature, the maximum being from the middle of July to the middle of September similar to the maximum of diarrhoea mortality, and in point of fact the deaths from tabes are mostly hastened by diarrhoea; the absolute minimum is from the end of December to the beginning of February.

The relation of phthisis to weather they have also delineated in a curve, and remark: "The absolute minimum occurs in the last week of September, after which it begins steadily to rise; in the middle of November it rises still more quickly; during the last three weeks of December it falls a little; rises again in the beginning of the year, and remains steady until the second week of March, when it rises to the annual maximum during March, April, and May. From the middle of July to the middle of November it is below the average. This is one of the most constant curves in its main features from year to year."

(344) Bacteriology and Pathology of Tuberculosis.

Those works are alone noticed which relate to the parasitic nature of the tuber culous virus. Other works on the etiology of tuberculosis are summarized in great part by Waldenburgh (Die Tuberculose, die Lungenshwindsucht u. Skrophulose. Berlin, 1869) and by Johne (Deutsche Zeit. f. Thiermedicin. IX Bd.).

It is known that Villemin, from his experiments on animals, expressed the view that tuberculosis could only be produced by a specific virus. This opinion was at first much contested, but shortly gained ground. Individual authors then maintained not

1 Journal of the Scottish Meteorological Society, July 1874, 1875.

only the specific nature of tuberculosis, but that it was also probable the tubercular virus was parasitic, e.g., Chauveau,1 Baumgarten, Ziegler, and others. There was no want also of researches recognizing the supposed parasite. Thus Zurn, had already found in the year 1872 in the tubercle of the cow, and in the inoculated tubercle of the rabbit, small punctiform molecules which he described as micro-cocci. Buhl 5 likewise maintained that in the cheesy masses and giant cells of tubercle, spherical and rod-shaped bacteria were present. Klebs resorted to cultures, and by means of "fractional cultivation" obtained cocci-like organisms, through the inoculation of which he produced tubercles in animals, which tubercles contained similar organisms. Schiller and Reinstadler 8 obtained the same results. Toussaint 9 also obtained from his cultures small cocci, mostly in pairs, the virulence of which increased with the number of successive generations. Aufrecht 10 found in tuberculosis short bacilli, the length of which were half as much again as the breadth; there were also two different kinds of micrococci. Deutschmann 11 lastly maintained that the cocci present in tuberculous pus, which indeed showed throughout the characters of the "monas tuberculosum" (Klebs), were not all of equal activity, only those contained in the deeper, more tenacious layers of the pus, containing cocci which could produce tubercle.

The researches quoted above, made by very imperfect methods, could not be confirmed, and still the nature of the tubercular virus remained unknown until at last Koch succeeded by his perfected method in discovering the parasite of tuberculosis, and established its etiological significance in a convincing manner.

In the first communication of Koch 12 on this subject a method of colouring the bacilli in sputum on microscopic glass covers, and in sections of hardened organs is described :—the preparation was

1 Rec. de Med. vet.

1872.

2 Berliner klin. Wochenserift. 1880.

3 Lehrbuch der allg. u. spec. Patholog. Anatomie. 1881.

4 Zoopathologische u. Zoophysiologische Untersuchungen. 1872.

5

Lungenentzündung, Tuberculose u. Schwindsucht. 2 Aufl. 1873.

6 Tageblatt d. Versammlung Deutsch Naturforscher u. Aertze in München. 1877;

Prager Medic. Wochenschrift. Nos. 42 and 43. 1877.

7 Archiv f. exper. Pathol. II. Band; Experimentelle u. histologische Untersuchungen über Entstehung u. Ursache der Skroph. u. tuber. Gelenksleiden. Stuttgart, 1880. 8 Archiv. f. exper. Pathol. II. Bd.

9 Comptes Rend. 1880. 10 Pathologische Mittheilungen. Magdeburg, 1881. 11 Centralblatt f. d. Medic. Wissenschaft. No. 18, 1881.

12 Berliner klin. Wochenschrift.

No. 16, 1882.