194 THE DISEASES OF DOMESTIC ANIMALS. 



the normal indentations of the bones — at least, they are found under 

 the periosteum. Tuberculosis also comes to pass in swine, rabbits, 

 Guinea-pigs, monkeys, and other animals. Does the same cause 

 work here as in man, the horse, or cow ? 



Again, etiologically speaking, we have several varieties of tuber- 

 culosis in man : First, hereditary causes ; second, idiopathic infec- 

 tion, from antecedent conditions, scrophulosis, cheesy conditions of 

 glands due to other causes ; third, infection from persons having 

 phthisis, by means of the aspiration of some specific irritans with 

 which they pollute the air ; and, fourth, the questionable infection 

 due to milk from tuberculous nurses, or cows. 



In cattle, we may briefly assume an almost similar line of causes. 



This will do for our present purpose. 



The tubercular neoplasm of glanders is, and always w^ill be, a 

 tubercle, having its peculiar cause, anatomical construction, and 

 course. 



Undoubtedly, in some unknown way, the physiological and ana- 

 tomical characteristics of the different species, as well as the varia- 

 tions in the cause, exert some influence upon the structure and 

 course of life of the tubercle. With regard to the structure and 

 nature of the tubercles in glanders, Yirchow says that " they are 

 formed chiefly by cellular proliferation. In the youngest neoplasm 

 I found large numbers of small, delicate cells, as well as numerous 

 nuclei ; in older tubercles, the cells are longer and contain nuclei ; 

 these cells are very abundant, composing the greater part of the 

 node. These cells undoubtedly proceed from the pre-existing ele- 

 ments, and especially in the mucosa? from the connective-tissue cells 

 of the mucosa and sub-mucosa. The greater the number of cells, 

 so much more dense and yellow is the node ; retrogressive processes 

 soon take place in the older nodes ; the cells undergo fatty meta- 

 morphosis, and break up and shrink. 



Leisering, who has made very extensive studies upon the neo- 

 plasmata of glanders, says : " In whatever form the neoplasms of 

 glanders may appear, the cells constitute their prevailing element. 

 They are generally found varying in size ; the majority bearing the 

 strongest resemblance to pus-cells ; others are from four to six times 

 larger. Aside from these, numerous free nuclei go to make up the 

 largest part of the node, as well as the cells of proliferating connect- 

 ive tissue. The neoplasms have a varying character, according to 

 the predominance of the cellular, or stromatous, intercellular tissue 

 over one another. The more rapid the development of the neo- 

 plasm, the more prominent the cellular elements ; on the contrary, 



