Contamination of Milk. 43 



ity of the milk. Backhaus 1 estimates that the germ life 

 in milk can be easily reduced to one-two thousandth of its 

 original number by using care in milking. He reports a 

 series of experiments covering two years in which milk 

 was secured that averaged less than 10,000 bacteria per cc., 

 while that secured under ordinary conditions averaged over 

 500,000. 



Fig. 13 gives an illustration as to what care in milking 

 will do in the way of eliminating bacteria. Fig. 12 shows 

 a gelatin plate seeded with the same quantity of milk that 

 was used in making the culture indicated by Fig. 13. The 

 first plate was inoculated with milk drawn under ordi- 

 nary conditions, the germ content of which was found to 

 be 15,500 bacteria per cc., while the sample secured under 

 as nearly aseptic conditions as possible (Fig. 13) contained 

 only 330 organisms in the same volume. 



Within recent years there has been more or less gener- 

 ally introduced into many cities, the custom of supplying 

 high grade milk that has been handled in a way so as to 

 diminish its germ content as much as possible. Milk of 

 this character is frequently known as u sanitary," u hygienic" 

 or "certified," the last term being used in connection with 

 a certification from veterinary authorities or boards of 

 health as to the freedom of animals from contagious dis- 

 ease. Frequently a numerical bacterial standard is exacted 

 as a pre-requisite to the recommendation of the board of 

 examining physicians. Thus, the Pediatric Society of 

 Philadelphia requires all children's milk that receives its 

 recommendation to have not more than 10,000 bacteria 

 per cc. Such a standard has its value in the scrupulous 

 cleanliness that must prevail in order to secure these re- 



1 Backhaus, Ber. Landw. Inst. Univ. Konigsberg, 1897, 2:12. 



