LIFE OF ELIE METCHNIKOFF 221 



hygiene and cleanliness, especially where suckling 

 infants are concerned. 



During the year 1912, he studied the intestinal flora 

 and the influence of divers food diets. He experi- 

 mented upon the rat, an omnivorous animal whose 

 mode of feeding resembles that of man. The rats 

 were divided into three lots, of which one was kept 

 to a meat diet, another to a vegetarian regime, 

 and the third to a mixture of both. The meat diet 

 was least favourable, and the best results obtained by 

 the mixed food. 



These observations led Metchnikoff to the study 

 of other problems intimately connected with the 

 same question. 



He undertook a series of researches in collabora- 

 tion with his pupils, MM. Berthelot and WoUman, on 

 the conditions which cause the diminution within the 

 organism of the toxic products of intestinal microbes. 

 They found that the quantity of these products was 

 very small in those animals which feed on vegetable 

 or fruit containing much sugar, such as carrots, 

 beetroot, dates, etc. This is explained by the fact 

 that the products of the decomposition of sugar are 

 acids which prevent the development of putrefying 

 microbes. But the sugar, rapidly absorbed by the 

 walls of the small intestine, only reaches the large 

 intestine in a much reduced quantity, for it is only 

 up to a certain point during its journey that the 

 cellulose of vegetables, rich in sugar, protects that 

 substance. The question, therefore, was to find the 

 means of making it reach the large intestine in 

 greater quantities. In the intestine of a normal 

 dog, an innocuous microbe was found, the Glycobacter 

 peptonicus, which decomposes starch into sugar. 



