NUMBER AND SOURCE OF BACTERIA IN MILK 25 1 



yard or fields. During milking, portions of these are 

 shed or rubbed off, and fall into the milk with hairs of 

 the animal: An enormous number of organisms may be 

 introduced in this manner, since old dried dung fre- 

 quently contains more than 1,500,000,000 per gram, 

 and many hundreds of thousands have been found 

 attached to single hairs on the flanks of dirty cows. Orr 

 obtained an average of 4752 colonies on agar plates 

 exposed underneath the udder for two minutes during 

 milking in the cowshed in winter. Where the udders 

 and flanks of the cows had been brushed, 1752 colonies 

 per plate were obtained, and in the case of four cows 

 which were well-groomed and the udders washed and 

 left slightly moist, similar plates left for the same period 

 of time showed an average of only 230 colonies. 



The milk from cows with brushed and washed udders 

 was found by Russell and Orr to contain 330 to 472 per 

 c.c., while the bacterial content of the milk of the mixed 

 ungroomed herd averaged from 1 1,000 to I 5,000 per c.c. 



Many of the bacteria in milk are derived from the 

 milkers. On many farms the milkers have no special 

 garment or overall to slip on when milking is to be 

 done, but milk in everyday clothing, which is frequently 

 the reverse of clean. The filthy, disgusting habit of 

 dipping the hands, often unwashed, into the milk when 

 milking is going on is a very common practice which leads 

 to bacterial contamination. The introduction of germs 

 of disease brought from the homes of the milkers is 

 likely to occur, and there is little doubt that scarlet 

 fever, and possibly the bacteria of typhoid fever and 

 diphtheria, have been transmitted to milk by the milker 

 and other human beings concerned with the management 

 of the cows and the handling of milk on the farm. 



