126 ANNUAL. REPORT OF THE Off. Doc. 



•jeuerations are likely to grow iii au exceediugly thin layer which 

 resembles ground glass closely. The optiiauiu temperaUire as well 

 as the thermal death point are praclicalJy the same. 



The human bacillus, as a rule, grows more easily aiid abundantly 

 Irom the first, and will grow well on glycerin agar in sub-cultures 

 made directly Irom the original growth on blood-serum. All at- 

 tempts to obtain a like result with the bovine organisms have failed. 



The morphologic distinctions tend to disappear also in the tis- 

 sues of susceptible animals. We may inoculate a typical bovine 

 culture, and in a very short time scrapimgs from the various orgaus 

 will show long and very much beaded bacilli. 



The most striking dissimilarity is, however, seen in the action of 

 the bacilli from tiie two sources on animals. i>y whatever method 

 of inoculation, the bovine bacillus, as a rule, possesses a very much 

 greater pathogenic power than the human bacillus for all animals 

 on which it has been tried, the only exceptions being possibly those 

 animals, like guinea-pigs and swine, which are so extremely suscep- 

 tible to both types that it is hard to draw any distinction between 

 them. This was the case with swine inoculated by feeding in our 

 own experiments, but Koch and Schiitz found that for swine also the 

 bovime bacillus was much more active. The list of asiimals for which 

 this increased virulence has been proven includes horses, cows, asses, 

 sheep, goats, dogs, cats, rabbits, guinea-pigs, and receutly the same 

 thing has been shown to hold true for man's relative, the monkey, by 

 de Joung de Schweinitz and Schroeder, and ourselves. 



In our own experiments two mookeys inoculated subcutaneously 

 with Culture L, obtained from milk, died on the thirty-seventh and 

 thirty-third days, while the corresponding pair of the same species, 

 and as nearly the same weight as possible, inoculated with Culture M, 

 from human sputum, lived hfty-four and ninety-six days, respectively, 

 the last being chloroformed in a moribund conditioo. Two other 

 monkeys which were inoculated by feeding five times with the same 

 cultures smeared on banana, lived forty-two and ninety days, respec- 

 tively. The postmortem examinations showed for the animals which 

 received the bovine cultures a more active invasion and more acute 

 process. 



What has been said concerning the greater pathogenic power of 

 the bovine organism has, I think, been proven beyond question to 

 be the rule. It must be borne in mind, however, that what we speak 

 of as virulence is a very variable quantity, no micro-organism being 

 known which always shows the same degree of pathogenicity. The 

 tubercle bacillus isolated from cattle varies in its pathogenic power 

 considerably, though not perhaps to such an extent as those obtained 

 from human sources. Among the latter we find some cultures which 



