GIL XXXIV.] BACTERIAL ACTION 525 



until the temperature is raised to 67 C. Other observers have con- 

 firmed the discovery of erepsin, but have found that it or a similar 

 enzyme is present in most tissues; it is most abundant in the 

 kidney (Vernon). 



Cohnheim has investigated the action of erepsin on a large 

 number of proteins; it acts energetically on proteoses, peptone, and 

 protamines: on histone, which occupies an intermediate place 

 between protamines and the other proteins, it has a slight action. 

 On the other native proteins it has no action, with the single excep- 

 tion of caseinogen, which is speedily broken up into simple sub- 

 stances ; thus opens up the interesting physiological possibility that 

 the suckling infant is able to digest its protein nutriment even if 

 pepsin and trypsin are absent. 



The bile, as .we shall find, has little or no digestive action by 

 itself, but combined with pancreatic juice it assists the latter in all 

 its actions. This is true for the digestion of starch and of protein, 

 but most markedly so for the digestion of fat. Occlusion of the bile- 

 duct by a gall-stone or by inflammation prevents bile entering the 

 duodenum. Under these circumstances the fceces contain a large 

 amount of undigested fat. 



The importance of the work of Pawlow, and the other physi- 

 ologists whose names have been mentioned, arises from the entirely 

 new light thrown upon the digestion process as a whole. We have 

 been too apt to think of the occurrences in the alimentary canal as a 

 series of isolated phenomena. We now see that each step follows in 

 an orderly manner as the result of the previous steps. For example, 

 the acid gastric juice reaches the small intestine, and there produces 

 secfetin from its forerunner ; the secretinis taken by the blood -stream 

 to the pancreas, where it excites a flow of pancreatic juice; this juice 

 arrives in the duodenum ready to act on starchy substances and on 

 fat. With the assistance of the bile, fatty acid is liberated which in 

 its turn forms more secretin, and so more pancreatic juice. The 

 pancreatic juice, however, cannot act on proteins without enterokinase, 

 which is supplied by the succus entericus ; this sets free the trypsin ; 

 and trypsin with the assistance of erepsin effectively carries out 

 digestive proteolysis. 



Bacterial Action. 



The gastric juice is an antiseptic ; the pancreatic juice is not. 

 An alkaline fluid like pancreatic juice is just the most suitable medium 

 for bacteria to flourish in. Even in an artificial digestion the fluid 

 is very soon putrid, unless special precautions to exclude or kill 

 bacteria are taken. It is often difficult to say where pancreatic 

 action ends and bacterial action begins, as many of the bacteria that 

 grow in the intestinal contents (having reached that situation in 



