INTRODUCTION 3 



obtain nutriment unless the complex compounds, pro- 

 teins, urea, and other nitrogenous bodies, which form 

 the important constituents of many manures, are broken 

 down into simpler ones through the agency of bacteria. 

 He sowed seeds in sterile soil free from nitrates, nitrites, 

 and ammonia, which was plentifully watered with sterile 

 milk and solutions of sugar and starch. These substances 

 underwent no change, and the seedlings dwindled and 

 died. As regards the higher animals divergent views 

 have been expressed. Pasteur considered that their life 

 also would probably be impossible without the presence 

 of bacteria in the intestinal tract. Nencki expressed the 

 opinion that this idea of Pasteur's was an erroneous one, 

 and his experiments in conjunction with Macfadyen and 

 Sieber l showed that any considerable decomposition of 

 the food by bacteria first takes place in the large intestine, 

 and that the digestive juices alone, without the co- 

 operation of bacteria, are able to prepare the constituents 

 of the food for absorption. Nuttall and Thierf elder 

 obtained unborn guinea-pigs by Caesarian section with 

 antiseptic precautions, and afterwards kept them in a 

 sterile environment and fed them on sterilised food. 

 Not only did the animals live, but they were even in a 

 more thriving condition than those naturally reared. 

 The intestinal tract was found to be sterile on the eighth 

 day. Schottelius, however, found that chickens reared 

 on sterile food were retarded in development, and experi- 

 ments by Moro on turtle larvse suggested that intestinal 

 bacteria are necessary for normal nutrition. It is quite 

 likely, however, that in these experiments the food used 

 was unsuitable, for at the time they were performed the 

 importance of " vitamines " for normal nutrition was 

 unknown, and Cohendy 2 succeeded in rearing chickens 



1 Journ, of Anat. and PhysioL, xxv, p. 390. 



2 Ann de VInst. Pasttur, xxvi, 1912, p. 106. 



