410 BACILLI IN CHRONIC INFECTIOUS DISEASES. 



tuberculous sputum. And that the tubercle bacillus is frequently, if 

 not usually, present in the milk of tuberculous cows has been proved 

 by the experiments of Bollinger, Hirschberger, Ernst, and others. 

 In Hirschberger's investigations milk from tuberculous cows induced 

 tuberculosis in guinea-pigs, when injected subcutaneously or into 

 the peritoneal cavity, in fifty-five per cent of the cases studied 

 (twenty). The conclusion is reached that the milk may contain tu- 

 bercle bacilli even when the udder of the cow is not involved. Ernst 

 also, from an examination of the milk from thirty-six tuberculous 

 cows in which the udder was apparently not involved, found the 

 tubercle bacillus by microscopical examination in five per cent of the 

 samples examined (one hundred and fourteen). 



The prevalence of tuberculosis among cattle is shown by numer- 

 ous investigations, and especially by the official inspections of 

 slaughtered animals made in Germany. Thus in Saxony, in the 

 year 1889, of 611,511 cattle examined 6,135 were found to be tubercu- 

 lous (about one per cent) ; in Berlin, 1887-1888, out of 130,733 ani- 

 mals slaughtered 4,300 were found to be tuberculous (3.2 per cent). 

 In view of the facts stated the great mortality from tubercular dis- 

 eases among children, many of whom are removed from other prob- 

 able sources of infection, is not difficult to understand, and the 

 practical and simple method of preventing infection in this way, af- 

 forded by the sterilization (by heat) of milk used as food for infants, 

 must commend itself to all. 



54. BACILLUS TUBERCULOSIS GALLINARUM. 



The researches of Maffucci (1889) and of Cadiot, Gilbert, and 

 Roger (1890) show that the bacillus obtained from spontaneous tu- 

 berculosis in chickens, although closely resembling the bacillus of 

 human tuberculosis, is not identical with it, varying especially in its 

 pathogenic power. This view is sustained by the observations of 

 Koch, who says in his address before the Tenth International Medi- 

 cal Congress (Berlin, 1890) : 



" The care which it is necessary to exercise in judging of the characters 

 which serve to differentiate bacteria, even those which are well known, I 

 have learned in the case of the tubercle bacillus This species is so definitely 

 characterized by its staining reactions, its growth in pure cultures, and its 

 pathogenic qualities, and indeed by each of these characters, that it seems 

 iiiij).>il>le to con found it with other species. Nevertheless in this case also 

 one should not rely upon a single one of the characters mentioned for de- 

 termining the species, but should follow the safe rule that all available 

 characters should he considered, and the identity of a certain bacterium 

 should only be regarded as demonstrated when it has been shown to corre- 

 spond in all of these particulars When I made my first researches with 

 reference to the tubercle bacillus I was controlled by this rule, and tested 

 tubercle bacilli from various sources, not only with reference to their stain- 

 ing reactions, but also with reference to their growth in culture media and 



