CHAPTER V 



THE BACTERIAL CONTENT OF MILK 



Numbers of Bacteria present in Milk The Milk of Towns. Natural Condi- 

 tions affecting Bacteria in Milk : (i) The Influence of Temperature. (2) 

 The Influence of Time. The Toxicity of Milk. (3) The Inter- relationship of 

 Bacteria in Milk and its Germicidal Power. Bacteria in Separated Milk. 

 Species of Bacteria present in Milk. 



It cannot be a surprise to anyone who considers the elementary 

 facts set forth in the first chapter to learn that the numbers of 

 bacteria present in milk reach, even under normal circumstances, 

 a very high figure. There is at present no fixed standard of 

 microbes in milk with which it is possible to compare results. A 

 host of observers have made quantitative investigations in which 

 milk has been obtained, collected for examination, removed, stored, 

 and examined, under widely varying circumstances. And as a 

 result it has been found as a matter of fact that many apparently 

 excellent milks contain more than 50,000 bacteria per c.c. 

 Many town milks contain hundreds of thousands and frequently 

 millions of bacteria per c.c.^ Owing, however, to differences of 

 nomenclature, classification, and mode of examination at present 

 existing in various countries, neither qualitative nor quantitative 

 estimations can as yet be of much permanent value. When a 

 common international standard is established, mathematical com- 

 putations will be of worth. The presence of large numbers of 



^ Gernhardt obtained 7,000,000 per c.c. ; Watson and Loveland estimated 

 50,000,000 to 1,000,000,000 per c.c. "at the time when the curdling of milk 

 begins " ; Schmelck found 2,800,000 per c.c. in Christiania milk ; Moore found 

 7,200 and 8,400 per c.c. in the first milk, and 546 and 504 in the last milk ; 

 Schweinitz found 200 organisms per c.c. in pasteurised milk, as many as 50,000 

 in "sanitary" milk, and 115,000 in ordinary city milk ; Schultz found 97,000 

 bacteria per c.c. in fore-milk, 9000 in middle milk, 500 in milk at close of 

 milking ; Sedgwick and Batchelder 2,300,000 (in Boston) ; Russell 35,000 to 

 275,000 in April milk in Madison, U.S.A., and 380,000 to 2,000,000 during 



116 



