532 



WILLIAM H. CHAMBERS 



growth in the uninoculated raw milk control and in the two in- 

 oculated samples, raw and heated, which were identical except 

 for the heating. The heated controls are not tabulated, for in 

 every case only a few surviving spore-formers developed during 

 the four-hour period of observation. 



The growth of Bad. coli in the milk of these two cows cor- 

 roborates the presence of a bactericidal property in their raw 

 milk which is not evident in the corresponding heated sample. 

 A comparison of the raw and heated milk samples inoculated 



TABLE 4 

 Growth of bacteria in milk, raw and inoculated with Bad. laclis-acidi, at 87 °C. 



I = Innumerable. 



with this organism (table 2), shows in every case a marked reduc- 

 tion of numbers of bacteria in raw milk and a rapid increase in 

 numbers in the heated milk. The action is positive, for it is 

 practically the same in two separate tests with cow 212, and is 

 more intense with cow 155, for the count went below the 100 

 dilution at 120 and 180 minutes. In the milk of cow 212 there 

 is a return of the growth to the normal logarithmic rate of multi- 

 plication, after 120 minutes. This germicidal action, as com- 

 pared to the growth in the heated milk, is illustrated more clearly 

 in chart 1 , in which the curves are plotted from the logarithms of 

 the averages of the raw and heated milk samples from table 2. 



