PANCREATIC DIGESTION 1 89 



the reproductive glands. It is claimed by some that all active organs 

 of the body produce hormones. 



The juice as obtained from a permanent fistula differs greatly in 

 its properties from the juice as obtained from temporary fistula, and 

 neither form of fluid possesses the properties of the normal fluid. Pan- 

 creatic juice collected by Glaessner from a natural fistula has been 

 found to be a colorless, clear, strongly alkaline fluid which foams readily. 

 It is further characterized by containing albumin, globulin, proteose, 

 and peptone; nucleoprotein is also present in traces. 1 The average 

 daily secretion of pancreatic juice is 650 c.c. and its specific gravity is 

 1.008. The fluid contains 1.3 per cent of solid matter and the freezing- 

 point is o.47C. The normal pancreatic secretion contains at least 

 four distinct enzymes. They are trypsin, a proteolytic enzyme; pan- 

 creatic amylase (amylopsin), an amylolytic 'enzyme; pancreatic lipase 

 (steapsin), a fat-splitting enzyme; and pancreatic rennin, a milk-coagu- 

 lating enzyme. 



The most important of the four enzymes of the pancreatic juice is 

 the proteolytic enzyme trypsin. This enzyme resembles pepsin in so 

 far as each has the power of breaking down protein material, but the 

 trypsin has much greater digestive power and is able to cause a more 

 complete decomposition of the complex protein molecule. In the 

 process of normal digestion the protein constituents of the diet are for 

 the most part transformed into proteoses (albumoses) and peptones 

 before coming in contact with the enzyme trypsin. This is not abso- 

 lutely essential, however, since trypsin possesses digestive activity suffi- 

 cient to transform unaltered native proteins and to produce from their 

 complex molecules comparatively simple fragments. Among the prod- 

 ucts of tryptic digestion are proteoses, peptones, peptides, leucine, tyrosine, 

 aspartic acid, glutamic acid, alanine, phenylalanine, glycocoll, cystine, 

 serine, valine, proline, oxyproline, isoleucine, arginine, lysine, histidine, 

 and tryptophane. (The crystalline forms of many of these products are 

 reproduced in Chapter IV.) Trypsin does not occur preformed in the 

 gland, but exists there as a zymogen called trypsinogen which bears the 

 same relation to trypsin that pepsinogen does to pepsin. Trypsin has 

 never been obtained in a pure form and therefore very little can be 

 stated definitely as to its nature, The enzyme is the most active in 

 alkaline solution but is also active in neutral or slightly acid solutions. 

 Trypsin is destroyed by mineral acids and may also be destroyed by 

 comparatively weak alkali (2 per cent sodium carbonate) if left in con- 

 tact for a sufficiently long time. Trypsinogen, on the other hand, is 

 more resistant to the actions of alkalis. In pancreatic digestion the pro- 



1 Glaessner: Zeilschrift fur physiologische Chemie, 40, 476, 1904. 



