470 Transactions of the Canadian Institute. [Vol. VII. 



milk to the factory. The results of this examination showed that the 

 mixed milk of each patron contained from 4,000,000 to 30,000,000 of 

 micro-organisms per c.c. Astonishingly large numbers (from 100,000 

 to 5,000,000) of the Colon bacillus were found in many samples. 



Having seen from this review of the bacterial content of European 

 and American milk supplies, let us now examine the sources of this 

 contamination. 



The bacteria which find their way into milk come from : — (i) The 

 fore-milk; (2) The animal and milker; (3) Dusty air; (4) Unclean 

 utensils. And, as Russell remarks, " the relative importance of these 

 various factors fluctuates in each individual instance." 



I. — Contamination from the Fore-Milk. {See Fig. i). 



The constant presence of bacteria in freshly-drawn milk is a matter 

 of considerable importance, and this fact helps to explain the ineffectual 

 attempts to obtain milk in commercial quantities uncontaminated by 

 bacteria. At the same time it has been but very recently that investi- 

 gations as to the number and nature of the organisms that gain access 

 to the milk through their localization and multiplication in the milk 

 ducts, have been made. The first recorded experiments are those of 

 Leopold Schultz^^ in 1892. He examined milk bacteriologically at the 

 first of the milking, in the middle of the milking and at its close. This 

 examination consisted merely in counting the number of bacteria 

 present, and as a result, the following figures were determined : — The 

 first milk contained from 55,000 to 97,200 germs per c.c; the middle 

 milk from 2,000 to 9,000 germs per c.c; and the last milk was in some 

 cases sterile, and sometimes contained about 500 germs per c.c. The 

 number of germs in the last milk, he says, depended upon the quickness 

 with which the milking was done. When done quickly, all the germs 

 were washed out, so that "the last milk was often, but not always, 

 sterile." 



Gernhardt^^ investigating the same subject found a larger number 

 in samples from the middle of the milking than at the beginning. Ta 

 explain this result, as well as to explain irregularities in the numbers, he 

 suggested that the bacteria made their way up through the milk-ducts 

 of the teats, through the cistern, and into the smaller ramifications of 

 the ducts which connect the cistern with the ultimate follicles. As 

 many of the colonies so formed are not easily removed, they are not 

 found in the first milk, but appear later when they have become broken, 

 up by the persistent movements of milking. 



