TUBERCULOSIS. 
533 
animals as soon as ten days when introduced directly into the cir¬ 
culation in five or six weeks when subcutaneously inoculated, 
and in from three to four months when associated with infectious 
animals. These facts have been well demonstrated by Koch in 
his numerous experiments. Animals that are not susceptible to 
this disease will succumb to the direct inoculation of large num¬ 
bers of the bacilli. The period of incubation is an uncertain one, 
as will be seen from the results of the experiments made by Koch, 
varying as regards the amount of virus entering the system, and 
the susceptibility of the animal. 
By artificial means this bacilli has been cultivated for eighteen 
months, through twenty-six successive breedings, and then found, 
by inoculation, to produce the morbid phenomena of tuberculosis? 
the same as when taken from an infected animal. This organism 
may gain its entrance into the system by circulation, from the 
mother, respiratory or digestive tracts, or through wounds on any 
part of the body. It has been well said that contagious diseases 
in general, and tuberculosis in particular, are very infrequent in 
habitations to which strange cattle are not admitted, and where 
vacancies are filled up by the home stock. 
The development of the disease depends upon the surround¬ 
ings, condition of the animal, the organ or tissue involved, and 
the amount of virus taken into the system. The first evidence of 
infection is an elevation of temperature, which often passes away 
in a few days unnoticed. 
The general condition of the animal will depend on the prog¬ 
ress that the disease has made so as to interfere with the func 
tions of the body. This will vary from the appearance of per¬ 
fect health to emaciation, with a rough, starey coat, and hide¬ 
bound. Among other symptoms, there is an enlargement of the 
external lymphatic glands of throat, neck and flank, and usually 
associated with disease in some of the internal organs. Again, 
there is lameness without any evidence of external cause, swelling 
of the joints, contraction of muscles of the neck, and abscesses 
along the bones. 
Cases often present themselves with a cough, more or less dis¬ 
charge from nostrils, hurried and labored respiration, or even dif- 
