CHAPTER VIII. 



THE PROCESSES OF DIGESTION AND RESORPTION. 



IN the preceding chapter we have considered the various digestive 

 fluids which are concerned in the transformation of those food- 

 stuffs that are incapable of resorption as such into material which 

 the body can utilize for purposes of nutrition, and we have seen that 

 the most important agents which are here concerned belong to the 

 class of the non-organized ferments. In the present chapter we 

 shall study the action of these various substances upon the clifferent 

 classes of food-stuffs collectively and in somewhat greater detail, 

 and shall incidentally also consider the resorption of the final prod- 

 ucts of digestion from the gastro-intestinal canal. 



THE DIGESTION OF THE CARBOHYDRATES. 



The digestion of the carbohydrates is essentially effected in the 

 small intestine through the agency of the amylolytic ferment of 

 the pancreas, ptyalin, and the inverting ferments maltase, lactase, 

 and invertin, which are in part also furnished by the pancreas, but 

 are principally found in the enteric juice. In those animals in 

 which ptyalin occurs in the saliva, amylolysis to a certain degree 

 also takes place in the mouth and continues in the stomach until 

 hydrochloric acid appears in the free state, when the ferment is 

 rapidly destroyed. In man, however, the salivary digestion only 

 plays a secondary role. It is true that the end-product of amylo- 

 lytic digestion, viz., maltose, can probably always be demonstrated 

 in the gastric contents, even after a few minutes following the 

 ingestion of starch ; but it must be borne in mind that the trans- 

 formation of starch into sugar does not take place in distinct 

 phases, but that one molecule of the substance may have already 

 been changed to maltose, while another is as yet unaffected. In 

 determining the intensity and the extent of amylolytic activity it 

 is hence unwarrantable to draw conclusions from mere qualitative 

 tests, and it is necessary to compare the amount of sugar which is 

 actually formed with the amount of starch that has been ingested. 



In the majority of the purely carnivorous animals, as has been 

 pointed out, the saliva contains no digestive ferments, and, in such, 

 carbohydrate digestion takes place exclusively in the small intestine. 



Through the action of the ptyalin of the pancreatic juice or of the 

 saliva, as the case may be, the insoluble starch is first transformed 

 into soluble starch or amidulin (amylodextrin), and is then succes- 



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