556 CLINICAL VETERINARY MEDICINE AND SURGERY. 



On reconsidering the distinctive characters just mentioned we see 

 that they are perhaps less marked than might at first appear. 



The general characters of the two bacilli are the same, and the 

 reactions they produce in the living organism are similar. In reply 

 to the objection that the histological characters of human tubercle 

 differ from those of tubercle in the Gallinacese we may point to the 

 still greater difference between the tubercles of the fowl and of the 

 pheasant ; in animals equally sensitive to both viruses, like the rabbit, 

 the histological features of the lesions are identical ; there is the 

 same formation of nodules, the same tendency to caseation. 



By studying the morphology of the two microbes they are seen to 

 be very similar ; the few differences which have been noted are secon- 

 dary, and equally marked variations are observed on comparing tuber- 

 culous bacilli from different members of the same species ; in man it is 

 not uncommon to find certain bacilli longer and more granular than 

 others. On the other hand, both in avian and in human bacilli the 

 great specific characteristics remain, especially the staining reactions, 

 which appear to us of infinitely greater importance than a morpho- 

 logical detail. 



Without being absolutely identical, cultures of the two bacilli offer 

 certain analogies ; the human bacillus can grow on glycerine media, and 

 in this respect tends to resemble the avian bacillus ; even though it 

 will not grow immediately, is this character sufficient to establish a 

 fundamental distinction ? Would not a simple variation of race suffice 

 to explain this difference ? 



We might make similar suggestions regarding the other differential 

 characters, but we hasten to consider those more particularly appro- 

 priate to our investigation — we mean the pathogenic properties. 



It is certain that different animals do not react in the same way to 

 both viruses; in this connection MM. Straus and Gamaleia lay stress 

 on the following fact which they have discovered : the dog readily 

 contracts human tuberculosis, but is proof against avian tuberculosis. 

 This fact is of considerable interest, but is, nevertheless, in our estima- 

 tion insufficient to establish a specific distinction. Equally marked 

 differences often exist between varieties of the same species ; the anthrax 

 bacillus kills the rabbit, while the first anthrax vaccine is without 

 action on it. To continue our comparison we might remark that from 

 the point of view of form and of cultures there is certainly as much 

 difference between the virulent anthrax bacillus and the attenuated 

 bacillus as between the bacillus of human and of avian tuberculosis. 



We do not think it advisable to rely on one or two differential 

 characters in attempting to solve this question, but to take into con- 



