du 
u. B. m’CURDY. 
almost impossible to detect dormant germs, which are innocu¬ 
ous until by some debilitating disease the animal’s vitality is 
lowered to such a degree that it is unable to further resist the 
otherwise harmless bacilli. 
Tuberculosis is due to a specific germ known as bacillus 
tuberculosis, which is the exciting cause in* all cases, and the 
disease is contracted by inhalation, ingestion, and circulation, 
though more commonly by ingestion and inhalation. hocal 
affections of the organs through which the germs pass are usu¬ 
ally the primary lesions presented and show different phases in 
different animals. It is of frequent occurrence that the organ 
caving passage to the germs remains unaltered, and that the 
morbid process starts in the neighboring ganglions (viz., 
bronchial and mesenteric) and later extends to the pleura and 
peritoneum. At the point where the bacilli are arrested they 
first determine a formation of miliary tubercles, which, by gath¬ 
ering, form pyramid-like masses. Sometimes these neoforma¬ 
tions remain as localized inflammatory centres or become calci¬ 
fied ; at other times they undergo a caseous degeneration in 
fibrous transformation ; in some instances they separate, become 
ulcerous and produce cavities. When they become isolated by 
connective-tissue prolification from the surrounding parenchyma, 
or if they undergo complete calcification, the tubercles may 
heal. In the majority of cases the process becomes general. 
It may take place : 
1. By Means of Lymphatics .—The ganglions which are next 
to the primary tubercles are first involved,—in pulmonary tu¬ 
berculosis the bronchial and mediastinal ganglions are involved ; 
in intestinal tuberculosis the mesenteric ganglions, the spleen, 
and the liver. 
2 . By Continuity or Contiguity of Tissue .—This is a mode 
of propagation which is specially observed in mucous mem¬ 
branes. A pulmonary tuberculous centre which opens into the 
bronchi may be determined successively tuberculosis of the 
bronchial, tracheal, and laryngeal mucous membrane, and deg¬ 
lutition of tuberculous matter may produce tuberculosis of the 
