98 ^lASTITIS OF THE COW 



The left half of the udder is somewhat more severely- 

 exposed to the infection than the right. The posterior 

 quarters are much more frequently infected than the an- 

 terior quarters. The anterior quarters are seldom infected. 

 Usually one or two quarters, not frequently more than that, 

 are affected. 



Embolic tuberculosis of the udder occurs in one of the 

 posterior quarters as a rule, and in addition to it, in the 

 anterior quarter on the same side, or the other posterior 

 quarter or in both of these, i.e., both posterior quarters 

 together with one anterior quarter. Less frequently there 

 are infected only one of the anterior quarters, or one pos- 

 terior quarter and the anterior quarter on the opposite side, 

 or all four quarters together. 



Lung-tuberculosis in calves is somewhat infrequent, but 

 is common in old cows. One may expect, therefore, that 

 udder-tuberculosis will occur principally in old animals. Of 

 72 cases of udder-tuberculosis : 1 animal ( 1 per cent. ) was 

 3 years old; 11 animals (15 per cent.) were 4 to 6 years old; 

 60 animals ( 84 per cent. ) were 7 years old or older. 



Secondary Infection by Teat-infection. — This is com- 

 paratively rare, but can occur nevertheless. A complica- 

 tion with chronic streptococcic infection appears to be the 

 most common. Its effect is such that the milk becomes 

 quickly altered and pus-like. This condition induces a 

 severe sclerosis which is inhibitive to the extension of 

 tubercles. In such an udder a few small tubercles are 

 observed in the indurated parts, while the surrounding 

 portions, which have not been affected by the streptococcic 

 infection, present numerous large tubercles. 



Acute milk-infection [parenchymatous mastitis], like 

 acute streptomycosis, staphylomycosis and colibacillosis, 

 may develop secondarily in chronic udder-tuberculosis and 

 then conceal the primary chronic condition by its intensity. 

 This complication appears to be quite rare. 



