76 DAIRY CHEMISTRY 



Unsanitary condition of milk may be due to one 

 or more of these or to other factors, the most fre- 

 quent causes of contamination being lack of care of 

 the animals, the milk, and the dairy utensils. 



Condition of the Animals as to Health. — A diseased 

 animal, as one suffering from advanced stages of 

 tuberculosis or from other disease, does not give 

 sound or wholesome milk. The variations in the 

 composition of the milk when cows are suffering 

 with disease are often slight, scarcely sufficient to 

 change the percentage composition of the fat, casein, 

 and albumin. A careful examination of the milk, 

 however, will usually show the presence of abnormal 

 bodies, products, of the disease germ many of which 

 are toxic in character. Milk should be fairly con- 

 stant in composition from day to day. When the 

 fat content is found to vary between wide limits, it 

 is frequently due to a diseased condition of the ani- 

 mal. Normal health is followed by fairly constant 

 composition of milk ; limited variations are to be 

 expected, but not wide ones. Sound health of the 

 animals is the first requisite in securing a milk sup- 

 ply of high sanitary condition. In some forms of 

 disease, the milk will show the presence of an abnor- 

 mal amount of urea, a white crystalline compound 

 formed from disintegration of the muscular tissues 

 of the body which have failed to be excreted and 

 carried off by the kidneys. In normal milk, this 

 compound is present to the extent of .001 per cent, 

 but in diseased milk it is frequently present in much 



