5! 



MILK AND THE PUBLIC HEALTH chap. 



These different investigations show the profound influence of 

 temperature upon the multiplication of bacteria in milk. For 

 milk kept at 0° C. no multiplication of any significance takes 

 place for many days; at 10° C. there is some increase, but 

 within a reasonable period it is negligible ; at 15° C. there is 

 a considerable increase, but one which is not inordinate ; while 

 at higher temperatures the contained bacteria multiply with 

 very great rapidity. 



C. The Behaviour of Pathogenic Bacteria in Milk and 

 Milk Products 



As every bacteriologist knows, sterile milk is a suitable 

 culture medium for the majority of pathogenic bacteria. In 

 ordinary market milk, any pathogenic bacteria present have, 

 however, to withstand the possible prejudicial effect of the 

 presence of a large number of other organisms which may be 

 better suited to their environment and whose products may 

 be inimical. The extent to which pathogenic bacteria will 

 live and multiply in milk cannot, therefore, be forecasted with 

 certainty, and a number of investigations have had to be 

 carried out to study the question. 



Eyre ^ studied the rate of multiplication of some of the 

 pathogenic bacteria in sterile milk. He was careful not to 

 use sterilised milk, but used milk obtained in a sterile condition 

 by drawing it from the healthy cow under aseptic conditions. 

 He obtained the following results : 



This table, as Eyre points out, fails to show the exact 

 course of events, and if the results of the examinations at 

 shorter periods of time are studied, a definite bactericidal 

 influence is shown. This is seen from the following table : 



' Journ. of State Medicine, 1904, xii. p. 728. 



