4IO Veterinary Medicine. 



liquids intimately mixed with the air by atomization. In these 

 cases lesions began in the lungs and bronchial and mediastinal 

 glands.*" 



Bacteriology. The bacillus tuberculosis, the essential cause of 

 tubercle, was demonstrated by Koch in 1882. It was at first 

 supposed to be peculiar in its indisposition and tardiness to take a 

 stain, and in its retention of the stain once imparted, even when 

 it is treated with acids. L,ater observations have shown that 

 these characteristics are common to certain other bacilli, notably 

 to those of leprosy, smegma, and to specimens found in timothy 

 hay and other grasses, cow dung, milk and butter. These fur- 

 nish sources of fallacy in the milk and butter especially, but 

 when the specimens examined are taken from the interior of a 

 tubercle, lymph gland or serous cavity the danger of error may 

 be practically ignored. What is quite as important is the fact 

 that the tubercle bacillus is subject to evolutionary changes in 

 adapting itself to a habitat in different genera of animals, and to 

 a le-sser extent in different parts of the same animal, by which its 

 pathogenesis is modified, but these variations do not materially 

 affect the staining qualities. Still more striking variations have 

 been found in old cultures, ovoid forms (Metchinkoff), club- 

 shaped microbes and filaments (Metchinkoff, Klein, etc.), branch- 

 ing filaments (Fi.schl, Coppen Jones), divergent club-shaped 

 groups, like actinomyces (Babes and I,evaditi). The last named, 

 seen in inoculated rabbits, have been held to establish a relation- 

 ship between the microbes of tuberculosis and actinomycosis, as 

 the club-shaped cells do not take the usual Ziehl-Neelsen stain 

 for tubercle bacilli, but the Birsch-Hirshfeld's actinomyces stain. 

 Apart from the rabbit such variations are not likely to prove 

 sources of fallacy in identification of the microbe. 



Morphology. As met with in the tubercle of man or ox the 

 bacillus is a minute rod with rounded ends, 1.5 to 3.5/x long, by 

 0.2/A in thickness. In the ox it is shorter and thicker on an 

 average than in man. They are usually solitary, but two and 

 exceptionally even three or four elements may be united. In 

 stained specimens unstained portions are frequently seen (spores ?) 

 When cultivated on blood serum there is a tendency to form 



* (From Report to the N. Y. Legislature, 1895. James Law.) 



