DIGESTION 35 



of an explosion resulting in a large number of frag- 

 ments scattered about, but instead it may be looked 

 upon as a kind of slow erosion whereby certain pro- 

 jecting pieces are rubbed or broken off. Secondly, 

 absorption takes place rapidly and the erosion products 

 have a tendency to disappear from the alimentary 

 canal. A knowledge of the thorough character of 

 intestinal digestion has been made possible through the 

 employment of the polyfistulous method devised by 

 London. Animals with a series of fistulas along the 

 intestinal tract were fed gliadin and from successive 

 openings the enteric contents were examined for the 

 quantity of tyrosine and glutamic acid present. It was 

 shown that in the duodenal contents 0.75 gram tyrosin 

 and 2.5 grams of glutamic acid were present, in the 

 jejunum were 1.1 gram tyrosin and 20.9 grams of 

 glutamic acid while the ileum yielded only a trace of 

 tyrosin and 33 grams of glutamic acid. Similar experi- 

 ments with casein and meat yielded comparable results. 

 From these observations it is quite evident that the 

 processes of digestion in the intestine are gradual in 

 nature but the rate of disintegration is much greater 

 than obtains in artificial digestion mixtures. The 

 apparent explanation for the slower rate of hydrolysis 

 in in vitro experiments is that the digestion enzymes 

 form compounds with the amino acids split off and thus 

 are rendered inactive. This inactivation probably does 

 not occur to any extent in the intestine because the 

 amino acids do not accumulate therein, undoubtedly 

 being absorbed almost as soon as they are split off. 



