CARBOHYDRATES. 63 



extract which he had inoculated with bacteria from the contents of the 

 paunch upon absorbent cotton-wool, the following products were formed: 

 carbonic acid, methane, and fatty acids (acetic, butyric, and valeric 

 acids). It is perfectly possible that the breaking down of the cellulose 

 takes place similarly in the intestinal canal. The behavior of cellulose 

 here has, however, never been entirely explained. It is also possible that 

 perhaps only a portion of the cellulose is decomposed in this way, while 

 another portion may be acted upon differently perhaps by means of the 

 epithelium of the canal itself, being transformed in such a way that it can 

 be absorbed. Not only the herbivora are capable of utilizing cellulose, but 

 the omnivora can make use of it at least to some extent. The investiga- 

 tions of v. Knieriem have shown that the human intestine is capable of 

 dissolving a part of the tender cellulose from young vegetables. As much 

 as forty per cent of the cellulose introduced into the system could not 

 be detected in the faeces. 1 



Cellulose, especially in animals possessing a long intestine, chiefly 

 the herbivora, but also the omnivora, plays still another characteristic 

 part, as the following experiments show. If rabbits are fed with food 

 containing no cellulose, they soon die. This is due to the fact that 

 when cellulose is left out of the nourishment the intestine no longer expe- 

 riences a certain mechanical irritation to which it has become accustomed. 

 On this account the peristalsis becomes retarded, then the contents of the 

 intestines accumulate, whereby putrefaction ensues, and eventually there 

 is inflammation of the bowels. That this explanation is correct, is shown 

 by the fact that the animals experimented with continue to live, if, instead 

 of the cellulose, the animals are fed with horn shavings which are perfectly 

 indigestible. 2 



The bacteria contained in the stomach and intestines attack not only 

 cellulose but other carbohydrates as well. For this reason, the breaking 

 down of the more complicated carbohydrates does not actually take place 

 so simply as has been depicted. On the other hand, the decomposition 

 brought about by means of bacteria is, in general, not very extensive, and 

 depends very much upon the external conditions. The products formed by 

 their action are chiefly lactic acid, formic acid, acetic acid, butyric acid, and 

 alcohol with evolution of carbon dioxide, hydrogen, and methane. 8 There 

 are, furthermore, other micro-organisms known, as, for example, Bacterium 4 

 thermo, which break down starch in very much the same way. as this is 

 accomplished by the diastase in saliva and pancreas, thus aiding the 

 conversion of amylum into sugar. 



1 Loc. tit. 



2 von Knieriem: loc. cit. 



3 Cf. H. Tappeiner: Z. Biol. 19, 228 (1883). 



4 J. Wortmann: Z. physiol. Chem. 6, 287 (1882). 



