CHAPTER VI 
INFLUENCE OF DISEASE UPON MILK 
Maw is susceptible to several of the specific infectious 
diseases of cattle viz: tuberculosis, aphthous fever or 
foot and mouth disease, cowpox, anthrax, rabies, and 
actinomycosis. Furthermore, mastitis, calf cholera, acute 
croupous and hemorrhagic enteritis (paracoli infection), 
septic metritis, and many suppurative conditions in cattle 
are caused by bacteria which are pathogenic for man. In 
certain non-bacterial affections, such as gastro-intestinal 
catarrh, the milk sometimes becomes unpalatable and, 
when ingested, may cause irritation of the gastro-intes- 
tinal tract, especially in children. 
The study of the conditions under which disease-pro- 
ducing organisms enter the milk and the effect of disease 
upon the milk secretion is one of the important divisions 
of milk hygiene. Bacteria or virus may be carried by the 
blood to the udder and be eliminated with the milk, or 
they may be excreted through one of the other normal 
open channels or discharged from wounds and enter the 
milk after it is drawn from the udder. The first method 
is called direct infection and the latter secondary infec- 
tion. There is no doubt that bacteria circulating in the 
blood may pass over into the milk when the tissue sepa- 
rating the udder alveoli and tubules from the capillaries 
is broken down by disease. Some investigators are of 
the opinion that this may also occur when the udder tissue 
is intact, but this view is disputed by others. When 
bacteria invade the udder through the teat canal, as 
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