EXTENT OF BACTERIAL CONTAMINATION. 45 



of bacterial contamination. The clothing that an ordinary 

 farmer wears becomes very soon loaded with bacteria and 

 these are quite sure to be detached by his motions during the 

 milking and to find their way into the milk pail. If his 

 hands are not clean it is inevitable that the friction of the 

 teats in the milking will rub from the hands the bacteria 

 which may be attached to them, and these will inevitably fall 

 into the milk. While this source of contamination is not so 

 great as some of the others, it is one which is frequently 

 of more importance than the others and one that should 

 be especially guarded against. It should always be remem- 

 bered that bacteria from man are more dangerous to human 

 health than those from the cow, and this applies not only to 

 the milker, but to all who subsequently handle the milk. 



EXTENT OF CONTAMINATION. 



The amount of contamination which will be found in any 

 sample of milk varies widely with conditions. From a dirty 

 stable and poorly kept cows milk will be produced that is 

 much more highly contaminated with bacteria than that from 

 a cleanly kept dairy. Actual experiment has shown that vari- 

 ations in extent of the contamination are very wide indeed. 

 By very strict precautions, such as can be adopted by an 

 extremely careful expert, the number of bacteria which find 

 their way into milk during the milking may be reduced to a 

 score or two in each cubic centimeter. Sometimes the num- 

 ber may be even less than this, although more commonly 

 even the greatest precautions will give a number somewhat 

 larger. From this small number the contamination is 

 greater with the decrease in the precautions that are taken. 

 In a common cleanly kept daify the number may be 1,000- 

 10,000 per cubic centimeter. In a dairy not so carefully 

 kept the number will rise to 30,000-50,000 per c.c., and 

 under very poor conditions the number may rise up to 300,000 

 -400,000 per c.c. in the milk as the result of the original con- 



