24 MILK AND THE PUBLIC HEALTH chap. 



found an increase. In one experiment the apparent increase 

 was about 70 per cent. From his experiments he concluded 

 that bacteria from the air or other source was not responsible, 

 and advanced the view that the increase was due to the breaking 

 down of the groups and clumps of bacteria which occur in 

 milk. Such breaking down would have the effect of con- 

 siderably increasing the number of colonies and so the apparent 

 germ-content. 



Heinemann, Luckhardt, and Hicks^ also experimented in 

 this direction, and found a considerable increase in the number 

 of bacteria after separation. As an average of 48 examinations 

 of 3 different samples of milk they found the milk before 

 separating to have a germ-content of 738, the separator milk 

 2130, the cream 132, and the reconstructed milk 1987 bac- 

 teria. They concluded that since the conditions under which 

 the separation took place were above reproach, as far as clean- 

 liness and handling were concerned, Severin's view was the 

 correct one, and the increase is due to the disassociation of 

 the aggregates of bacteria. 



Artificial milkers are discussed in Chapter XVI. As there 

 explained they are more likely to be a source of bacteria from 

 faulty cleaning than serve to diminish the germ-content of the 

 milk by removing sources of pollution. 



5. Contamination in Transit. — It is an extremely diffi- 

 cult thing to measure the amount of bacterial contamination 

 of milk which takes place in its transit from cowshed to milk 

 purveyor or consumer. The increase in the number of bac- 

 teria added from outside sources is obscured by the increase 

 due to the multiplication of the bacteria already in the milk. 

 It is not possible to give the extent of the contamination in 

 definite terms of bacteria added. In general, it may be said 

 that all the faulty conditions described in Chapter XV. 

 are sources of bacterial contamination of the milk, but the 

 extent of such bacterial additions must vary with the nature 

 of the condition and the opportunities offered for pollution. 

 The addition in transit of bacteria from outside is probably 

 trivial compared with the bacterial additions at the cowshed 

 and in the consumer's house. 



6. Bacteria added on the Purveyor's or Consumer's Premises. — 



^ Journ. of Infect. Diseases, 1910, vol. vii. p. 47. 



