66 Chapter III 



Pepsin was found in the urine by Briicke exactly forty years ago. 

 It is more frequently found in the morning urine, but is absent from 

 that passed immediately after the principal meal. Leo and Senator 1 

 found only traces of pepsin during the prolonged fast of the Italian 

 Cetti ; but the day he broke his fast they were able to demonstrate 

 the presence of a considerable quantity of this ferment in his urine. 



Delezenne and Froin, with the object of seeking the source of the 

 urinary pepsin, extirpated the stomach of a dog. After the animal 

 had recovered, they fed it well and examined its urine at different 

 periods of the day. By the methods which had shown the presence of 

 pepsin in all the normal dogs taken as controls they could never 

 discover the faintest trace of this diastase in the urine of the dog that 

 had been operated upon. On the other hand, the urine of a dog 

 whose stomach had simply been isolated, contained very much the same 

 quantity of pepsin as that of normal dogs. This experiment proved 

 among other things that the pepsin, before it could be eliminated by 

 the kidneys, must have been re-absorbed by the wall of the stomach. 

 [71] From these data, combined, it must therefore be admitted that the 

 pepsin found in the blood and which passes thence into the urine can 

 only be of gastric origin. As it serves no useful purpose in the organ- 

 ism we must conclude that a portion of the pepsin, secreted by the 

 stomach and not used for digestion, has been rejected as superfluous. 



The study of the digestive function of animals gives us information 

 on a large number of points of the highest importance for the com- 

 prehension of immunity. Intracellular digestion, a function so widely 

 distributed in the lower animals, is very intimately connected with the 

 phenomena which are observed when micro-organisms are destroyed in 

 the animal organism. Extracellular digestion furnishes us with informa- 

 tion concerning many of the features of progressive adaptation, similar 

 to those which are observed in connection with acquired immunity. 



When we examine the phenomena of intracellular digestion and 

 those of secretory digestion as a whole, we see that, in both, the 

 chemical processes are subjected to the influence of the living parts 

 of the organism. In the lower animals, it is the protoplasm of the 

 amoeboid cells which regulates the chemical processes in digestion ; 

 in the higher animals, this role is taken by a very complicated 

 apparatus, in which the nervous system plays a predominant part. 



1 Firchow's Archiv, 1893, Suppl. to Bd. cxxxi, S. 142. The question of urinary 

 ferments is summarised in Keubauer u, VogePs "Analyse des Harns," Wiesbaden, 

 10 to Aufl., 1898, S. 599. 



