432 SCIENCE PROGRESS 



juice obtained from a fistula, and rendered active by the addition 

 of 5 per cent, of the secretion of the intestine. 



The opening years of the present century were marked by 

 another discovery in the field of zymolysis, which has given rise 

 to a startling modification of our views of the mechanism of 

 proteid decomposition, and which threatens to revolutionise 

 our ideas of the relationship between the different proteases. 

 This discovery was made by Otto Cohnheim in the course of 

 some investigations on the fate of peptone, which though very 

 evident in the contents of the alimentary canal during digestion 

 cannot be detected in the blood, even in the vessels going from 

 the intestines. Apparently peptone is not absorbed as such by 

 the blood, and its fate has given rise to much speculation. In 

 the years 1880 and 1881 the view was put forward by many 

 physiologists that its disappearance is due to changes effected 

 by the intestinal mucous membrane, causing its reconversion 

 with a more stable form of proteid, possibly one of the proteids 

 of the blood plasma. Hofmeister held that such a conversion 

 was effected by the leucocytes, while Heidenhein and Shore 

 thought the action was due rather to the cells of the intestinal 

 epithelium in the region of its absorption. The general trend 

 of opinion was that these cells rather than the leucocytes were 

 responsible for its disappearance. 



In 1890 Neumeister, while not denying the possibility of a 

 reconstruction of proteid from the peptone, put forward the 

 view that a further splitting was possible. 



To this problem in 1901 Cohnheim directed his attention, 

 trying at the outset to discover the reconstructed proteid in the 

 epithelium of the intestine, but he failed to obtain any evidence 

 of its occurrence there. 



In view of the importance of the question a summary of 

 his experiments may be given. Digesting lean meat by pepsin 

 in the presence of oxalic acid he obtained the peptone with 

 which he began his work. After removal of the oxalic acid by 

 a salt of calcium he found his peptone to be practically free 

 from albumoses. Using this preparation he repeated Neu- 

 meister's experiments, and found that about one-third of the 

 small intestine of a cat altered o - 6 gm. of peptone in two hours 

 so completely that after removal of all coagulable proteids the 

 digested fluid no longer gave a biuret reaction. The method 

 he adopted to remove these proteids consisted in boiling the 



