THE SMALL INTESTINE 93 



peptic process which has been described. Acid which is 

 essential to digestion in the stomach is antagonistic to the 

 pancreatic type. Trypsin does its work best in a nearly 

 neutral mixture. In the normal course of events it acts 

 upon material already partly hydrolyzed, but it has the 

 power to carry through all its stages the digestion of native 

 protein. If the food is a solid, mere inspection reveals a 

 difference between peptic and tryptic solution. In the 

 former case there is marked swelling, as previously stated ; 

 in the latter there is progressive corrosion, a shredding or 

 honeycombing of the specimen. 



When chemical methods are employed in the study of 

 tryptic digestion, it is found to run a course roughly parallel 

 with that of the gastric digestion of proteins. Correspond- 

 ing intermediate bodies proteoses are described in both 

 instances, though it is said that some stages in the tryptic 

 process are passed so rapidly as to seem almost to be omit- 

 ted. What distinguishes the pancreatic proteolysis most 

 radically from the peptic is the facility with which the 

 peptones are broken down into still simpler bodies. We 

 have made the statement that these late cleavages take 

 place only very slowly under the influence of gastric juice. 

 So it becomes clear that trypsin is distinctly adapted to 

 follow after pepsin in the accomplishment of protein di- 

 gestion. 



Peptones are compounds which are simple by comparison 

 with standard proteins, but which are still too complex 

 to be given precise chemical formulas. When they are 

 hydrolyzed, most of the products come within the knowl- 

 edge of the organic chemist so definitely that their molecu- 

 lar structure can be confidently expressed. To the student 

 it must be admitted that such formulas do not appear 

 simple, but if he is disposed to resent the use of the word 

 he is to reflect that these molecules stand in some such rela- 

 tion to the original protein complex as the bits of the mosaic 

 bear to the whole design. It is with some such an idea 

 that the Germans have called them Bausteine, that is, 

 the building-stones, from which a new architecture can be 



