144 THE BACTERIAL CONTENT OF MILK 



and finally, that when these spores find themselves in a favourable 

 environment of temperature and nutriment, like the weakened and 

 unresisting tissues of an infant, they may in the course of an hour 

 or two germinate, become adult bacilli, and play their specific r61e. 

 We venture to think that the standard of milk sterilisation should 

 be almost entirely a standard based on the temperature which will 

 ensure the destruction of spores. For it is clear that the only 

 efificient milk sterilisation is one which will prove germicidal to 

 them. 



This excursion into the question of spores and sporulation may 

 appear to have led us far distant from the matter of inter-relation- 

 ship among bacteria in milk. But in fact it has not done so. For 

 it will now be apparent that the organisms in milk capable of 

 sporulation possess a powerful protective and resistant faculty 

 which enables them to survive a degree of competition or a short- 

 ness of pabulum to which non-sporulating organisms would 

 succumb. 



- The view that fresh milk possesses some germicidal power may 

 also be mentioned here. Some milk bacteriologists hold that there 

 exist in milk, as in blood, certain properties which are antagonistic 

 to the growth of organisms and that this is the explanation of a 

 decline which occurs in the number of bacteria soon after milk is 

 drawn. The theory seems not unreasonable, but we have not met 

 with any substantial evidence in support of it. 



Bacteria in Separated Milk 



In March and April 1899 we carried out an extended series of 

 experiments with the object of determining the quantity and 

 quality of the bacteria present in whole milk as drawn from the 

 cow under ordinary dairy conditions, and the constituent parts of 

 the milk after separation and setting. The first series of experi- 

 ment in respect of the set milk and set cream extended from 2nd 

 March when the milk was first drawn and set, to 5th April when it 

 became impossible to manipulate and examine the set cream 

 Fresh flasks were inoculated on March ist, 8th, 15th, 22nd, and 

 29th, and the progress of the colonies carefully observed. The 

 dilution throughout was i in 500, and of this dilution -i c.c. was 

 used for making the plates. (The plates throughout the experi- 



* Compare the survival of sporulating organisms in sewage. See Reports 

 to the London County Council on the Bacterial Treatment of Sewage, by H. C. 

 Houston, M.D., 1898 and 1899. 



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