256 MILK 



of fresh milk are these: A moderate decrease of bacteria, when 

 estimated by the colony count, is frequently observed in fresh 

 milk. The reduction is marked at 37 C., but of short duration, 

 lasting from four to six hours. At lower temperature the reduc- 

 tion is less definite, but is observable for a period of twelve or even 

 twenty-four hours. At 56 C. the reduction becomes less appar- 

 ent, and when the milk is heated to 68 C. or above no reduction 

 is noticeable. The decrease, in numbers varies with the pre- 

 dominant kind of bacteria present and with the source of the 

 milk. Typical lactic acid bacteria seem to be but slightly af- 

 fected by the restraining property of fresh milk and multiply 

 substantially from the moment the milk is drawn. 



Freezing seems to have no destructive influence upon the 

 germicidal property unless the time factor enters, and dilution of 

 milk renders it less apparent. 



The cause of the phenomenon usually called the germicidal 

 property of fresh cow's milk is probably the influence of several 

 factors, of which the following are perhaps the most important: 



1. The presence of antibodies; these are chiefly agglutinins and 

 bactericidal substances. 



2. The phagocytic action of leukocytes which operates chiefly 

 during the colostral period. 



3. The disappearance of micro-organisms that find in milk an 

 unsuitable environment. 



4. The fact that some bacteria do not seem to multiply from 

 the moment they enter a new environment, but hesitate for a 

 brief period. 



5. The presence of lecithin, which has a restraining action on 

 bacteria. 



Whatever the true cause or causes of the so-called germicidal 

 property of fresh milk may be, it seems certain that it is too feeble 

 to be of practical value. It cannot be used successfully as an 

 argument against the practice of heating milk for the purpose of 

 destroying pathogenic bacteria, even though antibodies are partly 

 destroyed at the temperature required for pasteurization. As a 

 matter of fact, the germicidal action disappears, as a rule, after 

 a lapse of twelve hours, so the keeping quality of milk is not 

 materially prolonged. 



BIBLIOGRAPHY 



Ayers and Johnson: United States Dept. of Agri., B. A. I., Bull. 126, Novem- 

 ber, 1910. 



Basenau: Arch. F. Hyg., 1895, vol. 23, p. 170. 

 v. Behring: Therapie der Gegenwart, 1904, vol. 4, p. 1. 

 Brudny: Cent. f. Bakt., Abt. 2, 1908, vol. 22, p. 193. 

 Coplans: Lancet, 1907, vol. 2, p. 1074. 

 Ehrlich and Brieger: Ztschr. f. Hyg., 1893, vol. 13, p. 336. 



