276 DIGESTION. 



into sugar, that we only rarely find it in the intestine, and then 

 merely in small quantities. Since, however, we always find sugar 

 in the intestine in association with starch, it is probable that the 

 dextrin, as such, is, like gum, absorbed only in very small quan- 

 tities. Although it can scarcely be doubted that a great part of 

 the starch taken with the food passes from the intestine into the 

 blood in the form of sugar, yet we may very readily convince 

 ourselves that a by no means inconsiderable quantity of starch is 

 metamorphosed in the small intestine into lactic acid, and in its 

 lower portions, but especially in the large intestine, into butyric 

 acid, and in these forms is more rapidly absorbed than as 

 sugar. 



Inulin is affected by the digestive fluids in precisely the same 

 manner as starch : indeed it may be concluded from the investi- 

 gations which I have instituted (which, however, were not of an 

 accurate quantitative character), that this substance undergoes 

 even a more rapid metamorphosis than ordinary starch. 



We now proceed to the consideration of sugar, and especially 

 of glucose, which, while it certainly demands our notice in conse- 

 quence of its frequent occurrence in articles of vegetable diet, is of 

 greater importance from its being, as we have just seen, the most 

 ordinary and normal metamorphic product of that most important 

 non-nitrogenous nutrient matter, starch. The question here at 

 once presents itself, does true glucose undergo any further 

 changes during the digestion of other substances or when digested 

 alone, or is it resorbed unchanged ? And after this question has 

 been answered, the following suggests itself, by what organs is 

 the glucose absorbed from the intestinal canal ? 



Many references have been made in the preceding pages to 

 the metamorphosis of glucose into lactic acid, butyric acid, and 

 fat; and hence we should scarcely have occasion to refer more 

 fully to the subject if we had not here to determine, at all events 

 approximately, the magnitude or extent of these metamorphoses. 

 It is commonly assumed that the sugar which is introduced into, or 

 first formed within the intestinal canal is absorbed without further 

 change, and very speedily, by the capillaries, a view which seems 

 to us very far from being satisfactorily established. That a portion 

 of the sugar before it is resorbed undergoes one or other of these 

 changes is almost generally acknowledged, but no direct investi- 

 gations have as yet been made regarding the quantity that is thus 

 altered, and it has commonly been regarded as extremely small. 

 The reason why it has been supposed that only a small quantity of 



