NON-SPORING BACILLI 299 



not prepared to deny that the transmutation of one type 

 into another may occur in nature, in view of the instances 

 in which one and the same human body yielded both 

 types. 



Replies to the Terms of Reference. The questions 

 referred to them for investigation and report were as 

 follows : 



(i) " Whether the disease in animals and in man is one and 

 the same. (2) Whether animals and man can be recipro- 

 cally infected with it. (3) Under what conditions, if at 

 all, the transmission of the disease from animals to man 

 takes place, and what are the circumstances favourable 

 or unfavourable to such transmission." 



i. Morphologically, as grown on serum, the human and 

 bovine types described are indistinguishable, but they are 

 appreciably different in respect of their cultural characters 

 and their capacity for causing disease in various species 

 of animals. The question of the identity or non-identity 

 of these two types clearly depends therefore upon the 

 importance which it is permissible to attach to their 

 cultural and pathogenic differences, and this depends on 

 the fixity or variability of the differences in question. 

 Though in the investigations no case was observed in which 

 the mode of growth of one type was so modified that 

 it was indistinguishable from the mode of growth of the 

 other type, yet the bacilli referred to as the bovine type 

 show so much variety among themselves as to luxuriance 

 of growth, that the gap which separates those of that group 

 which grow most luxuriantly from the human type, is 

 not a wide one. 



Again, as regards pathogenicity, it is more a matter of 

 degree than of difference. The bovine tubercle bacillus 

 produces a fatal tuberculosis in cattle, rabbits, guinea- 

 pigs, chimpanzees, monkeys, goats, and pigs. The human 

 tubercle bacillus readily produces a fatal tuberculosis in 

 guinea-pigs, chimpanzees, and monkeys, and in large 

 doses, only slight and non-progressive lesions in cattle, 

 goats, and pigs. Its effects on rabbits are not uniform, 

 for while in the majority of cases these animals are 

 only slightly affected, in some cases extensive and fatal 

 tuberculosis results. 



