102 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
of the salivary and lachrymal glands and pancreas. 
Numerous feeding experiments with milk and other sub- 
stances from rabid animals show that the virus is not 
absorbed, and that the disease is not produced, when the 
mucous membrane of the digestive tract is intact and the 
digestive functions are acting normally. In the upper 
part of the digestive tract, stratified squamous epithelium 
acts as a barrier to the entrance of the virus into the blood 
stream and when it reaches the stomach it is digested by 
the gastric juice. But when wounds are present in the 
mucous membrane of the lips, mouth or throat, or when 
the secretion of gastric juice is disturbed, the ingestion 
of milk containing the virus of rabies may produce the 
disease. Milk from cows affected with rabies must there- 
fore be regarded as dangerous. Whether the milk of 
infected cows contains the virus before symptoms of the 
disease appear, as is the case with the saliva of dogs, is 
not known. Until this question is determined it will be 
advisable not to use the milk of a cow which has been 
bitten by a rabid dog until it is determined that infection 
did not occur. 
ACTINOMYCOSIS 
Actinomycosis usually affects the maxille, tongue or 
other parts about the head, but it sometimes occurs in 
the udder, also in the lungs and other internal organs. 
When present in the udder it is usually of primary 
origin, i.¢e., the infection enters through the teat canal. 
Actinomycosis of the udder is generally indicated by the 
presence of one or several firm nodules of the size of a 
bean up to a hen’s egg in one or more quarters of the 
organ. These nodules consist of a thick wall of connec- 
tive tissue surrounding a purulent centre in which the 
actinomyces may be seen in the form of sulphur-yellow 
