CHAPTER IV 



THE BEHAVIOUR OF BACTERIA IN MILK 



IN Chapter II. it has been demonstrated that bacteria are 

 added to milk from very numerous sources, and in Chapter III. 

 the chief kinds so added have been considered. In view of 

 the fact that milk is rarely consumed directly after milking, 

 but only after the lapse of a more or less considerable period, 

 it is of great importance to consider the behaviour in milk of 

 the bacteria which have been added to it. 



The subject will be discussed in the following sub- 

 sections : 



A. The germicidal property of milk. 



B. The general behaviour of bacteria in milk under differ- 

 ent conditions both as a whole and for individual groups. 



C. The behaviour of pathogenic bacteria in milk. 



D. The thermal death -points of pathogenic bacteria in 

 milk. 



A. GERMICIDAL PROPERTY OF MILK 



It has been found when samples of freshly drawn milk 

 are examined at very short intervals, that not only may no 

 increase in the number of bacteria result for several hours, 

 but an actual decrease may at first be met with. This has 

 been ascribed to an inherent quality in the milk, and a germi- 

 cidal property has been evoked to explain it. Fokker in 

 1890 was the first to draw attention to this property of fresh 

 milk, and since then it has been the subject of a large number 

 of investigations. 



The following table, taken from Rosenau and McCoy's 



45 



