664 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



active enzyme at the moment of secretion, or it may be secreted in 

 inactive form and require the co-operation of some other substance 

 before it is capable of effecting its normal reaction. In such cases the 

 second substance is said to activate the enzyme. An example is 

 found in the case of the trypsin of the pancreatic secretion. 



PARTIAL LIST OF THE ENZYMES CONCERNED IN THE PROC- 

 ESSES OF DIGESTION AND NUTRITION. 



ENZYME. 



Ptyalin (sali- 

 vary diastase. 



A my lop s in 

 (pancreatic 

 diastase) . 



Liver diastase. 



Invertase. 

 Maltase. 



WHERE CHIEFLY 

 FOUND. 



Salivary secretion. 



Pancreatic 

 tion. 



secre- 



Liver. 



Small intestine. 



Small intestine, sal- 

 ivary and pan- 

 creatic secre- 

 tion, liver. 



Small intestine. 



Muscles? 



Pancreatic secre- 

 tion, fat tissues, 

 blood, etc. 



ACTION. 



Converts starch to sugar 



(maltose). 

 Converts starch to sugar 



(maltose) . 



Converts glycogen to dex- 



trose (maltose). 

 Converts cane-sugar to 



dextrose and levulose. 

 Converts maltose to dex- 



trose. 



Lactase. Small intestine. Converts lactose to dex- 



trose and galactose. 



Glycolytic? Muscles? Splits and oxidizes dex- 



trose. 



Splits neutral fats to fatty 

 acids and glycerin. 



Converts proteids to pep- 

 tones and proteoses. 



Splits proteids into sim- 

 pler crystalline prod- 

 ucts. 



Splits peptones into sim- 

 pler products. 



Split proteids into nitrog- 

 enous bases and amido- 

 bodies. 



Converts guanin to xan- 

 thin. 



Converts adenin to hypo- 

 xanthin. 



Cause oxidation of organic 

 substances. 



Decomposes hydrogen 

 peroxid. 



Chemical Composition of the Enzymes. It was formerly 

 believed that the enzymes belong to the group of proteids. They 

 are formed from living matter, and the solutions as usually prepared 

 give proteid reactions. Increased study, however, has made this belief 

 uncertain. The enzymes cling to the proteids when precipitated, 

 and it seems possible that the proteid reactions of their solutions may 



