FERMENTED MILK 485 



experiments with chickens and white rats, and the results if 

 accepted will make it necessary to revise the commonly accepted 

 views of the physiological actions of sour milk. Rettger found 

 that when chicks were fed milk not only was the percentage 

 of mortality materially reduced, but the rate of growth was 

 greatly increased. Practically the same results were obtained 

 whether sweet or sour milk was fed, and there was no appre- 

 ciable difference in the results obtained by feeding milk soured 

 by Bacillus bulgaricus and the common lactic forms. The 

 probable explanation of this fact was found in the experiments 

 with white rats, in which a study was made of the intestinal 

 bacterial flora during the feeding experiments. It was found 

 that when the rats were fed a diet which included milk, the 

 usual mixed bacterial flora of the intestines was replaced almost 

 completely by two types of bacteria which resemble the Ba- 

 cillus bulgaricus very closely, especially in their physiological 

 characteristics. Identical results were obtained when the 

 milk was displaced in the diet by milk-sugar. 



The conclusion seems obvious. The bacteria of the high- 

 acid type, which are apparently normally present in the intes- 

 tines, are stimulated by the unusual amount of milk-sugar fur- 

 nished by the milk diet, and multiply to such an extent that 

 the ordinary mixed flora is suppressed. 



The beneficial effect of a sour-milk diet is attributable, per- 

 haps, not so much to the bacteria contained in the milk as to 

 the milk itself, which provides material for an acid fermenta- 

 tion in the intestines. 



Milk is usually looked on as a nitrogenous food, but it should 

 be remembered that it contains about 5 per cent of lactose, a 

 carbohydrate which seems to be peculiarly adapted to bacterial 

 fermentation. 



Aside from the possible therapeutic value of fermented milks, 

 there can be no question that they are nutritious and refreshing 

 and that their use should be encouraged for their food value. 



