CHAPTER IX 



DIGESTION OF CARBOHYDRATES BLOOD SUGAR- 

 DIASTASIC FERMENTS 



CARBOHYDRATE DIGESTION 



TURNING away for a time from the processes of meta- 

 bolism which concern the proteins and nucleins, our path 

 leads into a new field stretching out interminably before 

 us the field of carbohydrate metabolism. Even though 

 the road be long, there comes a feeling of relief as we plod 

 the way, a feeling not unlike that the mountain climber ex- 

 periences as he reaches the tree-line on a heated day after 

 toiling painfully up through the high forest. Let the trail 

 before him be grievous as it will, he trudges blithely along, 

 with freer vision, no longer shut in on every side by the dusk 

 of the thickset woods. It really is a dusk which surrounds 

 us in the domain of protein metabolism. How could it be 

 otherwise? The chemical nature of the proteins is so un- 

 known, that in tracing their destinies in the depth of the liv- 

 ing body there can be expected no wealth of light. In taking 

 up the carbohydrates we at least are dealing with a chem- 

 ically well-defined material. 



We may at once undertake to follow the carbohydrates in 

 their transit through the body, beginning as in case of the 

 proteins with their fate in the digestive tract. 



Ptyalin. As is well known, the food in man and many of 

 the animals is at once mixed in the mouth with a diastasio 

 (carbohydrate splitting) secretion, the saliva. Because of 

 the fact that the hydrochloric acid of the stomach inhibits the 

 glycogenic action of ptyalin even when in relatively low 

 concentration and destroys the ferment entirely when in 

 higher concentration the opinion of many has been and is 

 now that ptyalin action is of comparatively little importance 

 and is quickly terminated when the food arrives in the stom- 

 ach. As a matter of fact, however, this cannot be the case. 



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