MILK 45 
minute quantity could be eliminated in the milk. When 
it is considered in addition that the milk secretion ceases 
in severely affected animals, the danger from toxins 
eliminated in the milk is very slight. Toxins may be 
produced by bacteria growing in milk after it is drawn 
from the udder. There is evidence to show that toxins 
are very readily absorbed through the gastro-intestinal 
mucous membrane of young animals. Toxins in milk 
from a different species are absorbed with much less 
facility than when the milk is from the same species. 
Diphtheria and tetanus toxins have been given to adult 
animals by the mouth in large quantities without any 
harmful effect, the toxins apparently being split up in 
the process of digestion like other proteids. These, how- 
ever, are soluble toxins (exogenous) which are more 
susceptible to chemicals and ferments than endotoxins. 
What may happen when the digestive processes are de- 
ranged, or when wounds are present in the mucous mem- 
brane, is not known. Milk from animals affected with 
rabies contains the virus of the disease, but such milk does 
not produce rabies when ingested if the mucous mem- 
brane of the digestive tract is intact and the gastric secre- 
tion is normal. 
Aggressins and other substances which inhibit the 
protective reaction of the body against the action of bac- 
teria and their toxins have also been demonstrated in 
milk. 
CLASSES OR GRADES OF MARKET MILK 
Until quite recently no effort was made to establish 
uniform grades or classes of milk. In some instances, 
the terms sanitary milk, hygienic milk, aérated milk, 
baby’s milk, nursery milk, etc., have been applied by dis- 
tributers to some of the milk sold by them, but these 
