BOVINE TUBERCULOSIS 361 



THE IDENTITY OR NON-IDENTITY AND INTERTRANSMISSI- 

 BILITY OF TUBERCLE BACILLI FROM VARIOUS SOURCES. 



Bovine Tuberculosis. When Robert Koch, in 1882, made public 

 his work in connection with the discovery of the tubercle bacillus he 

 believed that tuberculosis of man and animals was an absolutely 

 identical disease and that tubercle bacilli, no matter from what 

 source they were derived, were virtually identical in each and every 

 respect. Smith, in 1896, was the first to call attention to the fact 

 that tubercle bacilli from human tubercular sputum and those 

 derived from bovine tubercular lesions present certain differences in 

 their morphology, biology, and virulency toward various animals. A 

 more extensive communication concerning this work followed in 1898, 

 and another report was published in 1905. Smith's work as to differ- 

 ences in virulency toward domestic animals has since been confirmed 

 by Dinwiddie and others, and it has been established that tubercle 

 bacilli from bovine sources are generally short, straight, and cylindrical 

 in outline. At first they grow rather poorly on artificial media, are less 

 influenced by variations in the composition of the medium, and tend 

 to remain short when grown on artificial media for a number of genera- 

 tions. Bacilli derived from human tubercular sputum, on the other 

 hand, are generally more slender from the beginning, often curved. 

 They grow much more abundantly in first generations on artificial 

 media and show a tendency to remain slender or to become so if they 

 did not show this form in a decided manner from the beginning. 

 Mohler and Washburn, in a comparative study of tubercle bacilli from 

 varied sources, have come to the following conclusions as to a certain 

 plastic variability in their morphologic features, and say : 



"While certain peculiarities of growth, morphology, and patho- 

 genesis are observed with a fair degree of constancy in bacilli of 

 human origin, nevertheless these characteristics are not universal, 

 and notable exceptions are observed which would confuse those who 

 would attempt to establish their origin by means of such character- 

 istics. A similar degree of constancy in the morphologic, biologic, 

 and pathogenic characters of the bovine bacillus is generally noted; 

 but a certain range of differences has been observed, which, though 

 apparently more limited than for the human bacillus, is nevertheless 

 suggestive of aberrant forms." 



An important biologic difference in the action of human and bovine 

 tubercle bacilli in changing the reaction of the culture medium is 

 described by Smith as follows : "When flasks of glycerin bouillon in 

 layers 1 J to 2J centimeters deep are inoculated with scales of tubercle 

 bacilli from glycerin-agar cultures the floating masses soon begin to 

 expand, and after one or two months a complete membrane will have 

 formed over the relatively clear bouillon. The bacillar masses which 

 fall to the bottom at the outset increase but slightly in size." This 



