346 MILK AND ITS HYGIENIC RELATIONS 



CHAPTER XV 



ON THE PRESENCE IN MILK OF CERTAIN ORGANISMS LIABLE TO 

 CAUSE DISEASE, WITH NOTES ON MILK-BORNE EPIDEMICS 



A. On the Presence of Streptococci in Milk. The occurrence of 

 streptococci in milk has been already mentioned in Chap. VII, 

 when their possible connection with a high cell count was 

 discussed. It is necessary here to consider the prevalence of these 

 organisms, and to determine, if possible, whether, when present, 

 they must be regarded as harmful or if their presence may be 

 neglected. 



Prevalence of Streptococci. Numerous investigators have 

 examined large numbers of samples of milk in different towns for 

 the presence of streptococci. Speaking generally, it may be said 

 that wherever such systematic examination has been carried out, 

 a high percentage of the samples examined have been shown to 

 contain streptococci. 



Bergey found that 80 per cent, of the samples of market milk 

 investigated by him contained streptococci. In milk obtained 

 from four of the best dairies streptococci were absent in all the 

 samples examined from two of the farms, and present in 6-25 per 

 cent, and 28-57 per cent, respectively of the samples from the 

 remaining farms. 



Bnining examined the market milk in Leipzig, and showed 

 that 93 per cent, of all the samples taken showed streptococci. 

 These streptococci did not present the same characteristics, but 

 could be roughly classed under two headings : 



1. Those which were gram -positive, thick in appearance, and 

 formed in short chains ; 



2. Those which were gram-negative and arranged in diplococcic 

 order. 



Kaiser examined the milk in Gratz, and found that in the period 

 from November 22, 1904, to June 27, 1905, 76-6 per cent, of all 

 the samples examined contained streptococci. 



Campbell, working in Philadelphia in 1909 in connection with 

 the enumeration of leucocytes, found streptococci present in all 

 the samples of market milk examined (twenty). 



Ernst, working in Munich, stated in 1909 that in 1840 samples 

 examined by him, all contained streptococci. 



Savage demonstrated the presence of streptococci in 47 per 

 cent, of the samples of milk examined by him, when the centri- 

 fugalised deposit was brushed over agar plates. In eleven samples 



