Xkw York Agricultural Experiment Station. 125 



sidered in connection with any study of the milk flora hut its im- 

 portance is probably greatest in samples of freshly drawn milk. 



Bacteria are most abundant in the first few streams or fore- 

 milk, are distinctly less abundant during the main portion of the 

 milking and again become more abundant in the strippings. As 

 a result of this relationship a fairly close approximation of the 

 germ content of the entire flow of milk can be obtained by examin- 

 ing the strippings. Samples taken at this stage of the milking 

 are especially satisfactory as a basis for study of the udder flora. 



The germ content was found to be unequally distributed in the 

 udder, the back quarters having about three times as many germs 

 per cubic centimeter as the front quarters. The average of 1,230 

 samples was 428 per cc, but as the back quarters furnish more 

 milk than the front the average germ content in milk which can be 

 ascribed to the udder content will be approximately 500 per cc. Only 

 8 per ct. of the samples had a germ content of over 1,000 per cc. 



The connection between the period of lactation and the germ 

 content was not very marked. The colostrum showed a slightly 

 higher and the milk of the twelfth month a slightly lower content 

 than the intervening periods. 



The age of the cow likewise was not found to exert any ap- 

 preciable effect upon the germ content of the udder 



The kinds of organisms present in over 900 samples of milk 

 were studied and 71 groups described as members of the udder 

 flora. No organisms producing spores and no motile forms were 

 found. Seventy-five per ct. of the forms were micrococci but only 

 two streptococci were isolated. The need of free oxygen was so 

 great that 80 per ct. of the forms were not able to produce tur- 

 bidity in the closed arm of the fermentation tube. Gelatin was 

 liquefied by 55 per ct. of the forms and digestion of milk was 

 evident in cultures of about one-half of these forms, the remainder 

 probably liquefying too slowly to be determined by this compara- 

 tively crude method. No gas was formed in fermentation tubes 

 in the presence of dextrose, lactose, saccharose or glycerin but 

 acid was formed in percentages varying from 89 to 21 per ct. of 

 the forms with the different sugars. Nitrates were reduced by 

 59 per ct. of the forms and starch was attacked by 20 per ct. The 

 Gram stain was positive with 96 per ct. 



