A NUTRITIONAL STUDY OF INSECTS 71 



In 1896 to 1897 the experiment was repeated, the gain in weight 

 in eleven to thirteen days was almost normal, being 108 to 132 in- 

 stead of 130 to 180 grams. In a third paper ('97) the authors 

 experimented mth the hen's egg and found that it was not ster- 

 ile; they also summed up their pre\T.ous work in the conclusion 

 that animals just born do not grow well in the absence of micro- 

 organisms. Schottelius interprets the increase in the weight due 

 of guinea-pigs in these experiments as due to the coagulation of 

 caseinous material, from the milk, on the lining of the digestive 

 tract. This author used hen's eggs as material to sterilize, but 

 after a brilhant series of experiments ('99, '02, '08) has arrived at 

 the conclusion that normal life without bacteria is impossible, as 

 all the sterile individuals reared are retarded and stunted. Mme. 

 Metchnikoff ('01) and Moro ('05) obtained similar results with tad- 

 poles. In 1908 Tibbert, from theoretical considerations, came to 

 the conclusion that higher organisms cannot live in the absence of 

 microorganisms because each species of animal harbors definite 

 numbers and species of bacteria. Metchnikoff, Weinberg, Po- 

 zerski, Distaso, and Berthelot ('09), on the other hand, reared 

 the fruit bat Pteropus medius to normal size under practically 

 aseptic conditions, and Cohendy ('12) kept chicks alive in an- 

 aseptic condition from twelve to forty days. Cohendy's .con- 

 clusions are as follows: 



La vie sans microbe est possible pour un vertebre — le poulet — pourvu 

 normalement d'une riche flore microbienne. 



Cette vie aseptique n'entraine par elle-meme aucune decheance de 

 I'organisme. 



Kianigin ('17) has recently reopened this question by a 

 review of all the literature. At first sight it appears incom- 

 prehensible that aseptic life should be so difficult when the 

 greatest quantity of microorganisms is located in the non-diges- 

 tive portions of the digestive tract. Metchnikoff ('09) points out, 

 however, that the digestive powers of newly born are much 

 weaker than those of older animals. The increasing number of 

 cases of organisms which can be raised aseptically indicates that 

 an aseptic existence may be possible in the majority of cases. 



