64 LECTURE IV. 



The question has often been raised as to whether the micro-organisms 

 of the alimentary canal are absolutely necessary for the perfect digestion 

 of the food, or whether they should be regarded as true parasites. To 

 decide this point, Nuttall and Thierf elder 1 have made the following experi- 

 ment: By Caesarean section, they removed guinea pigs from the uterus 

 of the mother shortly before their normal birth, taking most careful anti- 

 septic precautions, and placing them in a sterilized cage. Guinea pigs, 

 unlike most of the related animals, come into the world in such a developed 

 state that they are able to assimilate properly the food of the adult. It 

 was found possible, as proved by later examination, to keep these little 

 pigs perfectly sterile during the entire experiment (eight days) and to feed 

 them with sterile food, crackers and milk, in a sterile environment. The 

 animals experimented with gained in weight normally, thus proving that 

 the animal organism could thrive when bacteria were absent. These 

 experiments were especially valuable because they were performed with 

 animals which are particularly likely to be infested with bacteria from 

 their vegetable food. It may be said, on the other hand, however, that 

 the experiment merely shows that guinea pigs can subsist upon crackers 

 and milk in the absence of bacteria, but it does not necessarily follow that 

 the result would have been the same if a food rich in cellulose had been 

 fed them. 



Schottelius 2 has arrived at quite different results from those of Nuttall 

 and Thierf elder. He chose for his experiments chickens which were 

 hatched under sterile conditions, kept in sterile places, and fed with sterile 

 food. These animals, although they ate abundantly, had continuous 

 hunger, and declined about as quickly as a starving animal. As soon as 

 bacteria from hen faeces were mixed with the food the animals revived and 

 increased in weight. Recently Moro 3 has carried out similar experiments 

 with the larvae of the mud-frog (Pelobates juscus). He was able to keep 

 them sterile for thirty-six days. It was found, however, that if the sterile 

 larvae were placed in water containing the faeces of the mother, the 

 increase in weight and general development was much more rapid than 

 was the case with larvae kept sterile. 



In discussing the carbohydrates we have mentioned the fact that the 

 five-carbon sugars, the pentoses or their condensation products the pen- 

 tosans which are so widely distributed in the vegetable kingdom, are not 

 unimportant forms of nutriment, especially in the case of the herbivora. 

 The researches of Stone 4 and of Weiske 5 have shown that the herbivora 



Z. physiol. Chem. 21, 109 (1895-96); 22, 62 (1896-97). 



Arch. Hyg. 34, 210 (1899), and 42, 48 (1902). 



Jahrb. fur Kinderheilkunde, 62, H. 4 (1905). 



Am. Chem. J. 14, 9 (1902). 



Z. physiol. Chem. 20, 489 (1895). 



