THE RELATION OF MICROORGANISMS TO MILK 473 



The high bacterial count in any lot of milk may be the result of any 

 one of these conditions or a combination of them. A high count means 

 that there has been carelessness either in the production, resulting in 

 high initial contamination, or in the subsequent handling permitting a 

 rapid multiplication of the organisms, or that the milk is old. 



On the other hand, milk with a low germ content can be obtained 

 only where the original contamination is small and the milk has been 

 held at low temperatures. A low count, therefore, means care both in 

 the production and later handling of the milk. 



While the germ content may be regarded as a general index to the 

 care the milk has received, it may not at all indicate its wholesomeness. 

 A high count may be the result of the rapid growth of the lactic bacteria, 

 in which case the milk may be perfectly safe and wholesome. On the 

 other hand, the count maybe quite small but contain pathogenic species. 

 The bacteria count is valuable as showing the sanitary conditions of 

 production and handling, but much care should be used in the inter- 

 pretation of such results. In some ways a direct microscopic examina- 

 tion of the milk sediment is much more satisfactory. The skilled 

 analyst can recognize certain types which may indicate the sanitary 

 quality of the milk. With sufficient experience one can recognize strep- 

 tococci, certain other groups and leucocytes. The presence and abun- 

 dance of one or more of these groups may indicate the nature of the 

 original contamination and the existence of diseases in the udders of 

 cows. If rightly interpreted the information thus obtained is of much 

 value. The weakness of this method lies in the fact that it is not 

 possible to recognize all types of disease organisms. In a smear prepa- 

 ration it is not possible to differentiate between pathogenic and non- 

 pathogenic streptococci or between B. coli and certain other types. 

 The presence of unusual numbers of streptococci and pus cells may 

 indicate the existence of disease in the cows and when this condition is 

 found* in the milk it is often possible to trace it back to the farm, lo- 

 cate the diseased cow and prevent her milk from being used for human 

 consumption. 



The tendency at present is to combine the quantitative and quali- 

 tative analyses and the results thus obtained in the hands of the careful 

 worker are of much practical value in controlling the quality of a city's 

 milk supply. 



