Contamination of Milk. 33 



ger which does obtain directly from the animal, and which 

 to some extent is modified by the nature of the food par- 

 taken, is due to the fecal matter that is voided from the 

 intestine. Under careless conditions this is permitted to 

 soil the flanks and udder of the animal. In a dried state 

 it is readily dislodged by the movements of milking and so 

 falls into the open milk pail. The nature of the food con- 

 sumed modifies to some extent the character and consist- 

 ency of the manure, physically as well as bacteriologically. 

 The modern use of a more nitrogenous ration than for- 

 merly has resulted in the production of a softer, more fluid 

 manure, which is more likely to soil the coat of the ani- 

 mal. The same is true with animals on pasture in com- 

 parison with those fed dry fodder. 



Wiithrich and Freudenreich * find a markedly higher 

 germ content in manure where animals are given dry 

 feed than where kept on grass. They found as many as 

 375,000,000 bacteria per gram in fresh manure, the major- 

 ity of which consisted of B. coli communis, the hay bacillus, 

 and other species able to peptonize casein. 



Organisms of this type are more abundant in winter 

 milk than in summer, as the opportunity for infection is 

 greatly increased by closer housing. 



The nature of the animal's coat favors greatly the re- 

 tention of dirt and dust. Cows wading in slime-covered 

 pools may cover the udder with material teeming with bac- 

 teria, which falls as an impalpable powder when dry. The 

 danger which may come from the introduction of such 

 matter is readily seen if hairs are removed from the coat 

 of the animal and laid on the surface of a sterile gelatin 

 plate as in Fig. 9. Almost invariably, a number of colo- 



' Cent. f. Bakt., II. Abt. 1895, 1:8?3. 



3 



