iv DIGESTION IN THE INTESTINE 227 



nitrogenous bodies of the aromatic series, e.g. indole, scatole, 

 phenol, paracresol, phenyl-propionic acid, and other aromatic acids 

 (Nencki), with simultaneous development of gas (sulphuretted 

 hydrogen, carbonic acid, methane, hydrogen). When they act on 

 gelatin, the intestinal microbes also produce glycocoll or glycine 

 along with much leucine, ammonia, lactic acid, butyric acid, and 

 carbonic acid. Besides these well-defined chemical compounds, 

 the so-called ptomaines appear when the intestinal microbes are 

 cultivated on gelatin ; these are little-known alkaloids, which 

 often act as powerful toxins. 1 



It is obvious that if all these putrefactive decompositions of 

 protein occurred inside the intestine with the same intensity as 

 they do outside the body, they would not only fail to benefit the 

 organism but would be actively injurious, and mankind would be 

 in constant danger of fatal auto-intoxication. Maly expressed 

 the opinion that the limitation of our existence depends on a 

 series of continual and gradual modifications to which the body is 

 subject owing to the putrefactive processes of the intestine, and 

 repeats with Brieger, Homo non vivit quia putrescit. We believe 

 (as will presently be shown) that the true cause of natural death is 

 neither extrinsic, nor to be sought in the intestinal contents, but 

 is seated higher, i.e. in the intrinsic nature of the living protoplasm 

 and its metabolism. To Brieger's apothegm we would oppose 

 the affirmation that Homo morietur quia vivit. 



There must therefore be conditions in the normal state of the 

 intestine which tend to keep the putrefactive processes due to 

 microbes within narrow bounds, so that they shall subserve the 

 digestive functions of the secretory enzymes and not damage the 

 economy of the system. It is only necessary to assume that the 

 food-stuffs are absorbed as fast as they are sufficiently digested, 

 and carried away from the intestine, which removes them from 

 the further action of the bacteria. The acidity of the gastric 

 juice, again, fulfils an important bactericidal function in limiting 

 the entrance of germs into the intestine ; while the acid reaction 

 is also preserved in the jejunum and ileum, as far as the ileo-caecal 

 valve, not by hydrochloric acid, but by the organic acids developed 

 by the bacteria. These create a medium unfavourable to the 

 putrid decomposition of protein, and the excessive multiplication 

 of bacteria. 



The observations made on man in cases of fistula of the upper 

 part of the small intestine confirm the importance of the com- 

 plementary digestive function accomplished by the intestinal 

 bacteria, as also the natural limitation of the putrefactive 

 processes which go on in the intestine. 



1 The recent work of Dale and Barger and others has added considerably to our 

 knowledge of the origin and nature of these bodies, and their papers should be 

 consulted. (Journ. of PhysioL, 1908-11.) 



