GUM STARCH. 69 



existing in a state complete for description, yet, even as it 

 stands, it deserves a close attention. 



The proximate principles which have chiefly drawn notice 

 under this point of view have been termed carbo-hydrates, 

 such as celluline or cellulose, gum, starch, and the several 

 forms of sugar. Celluline, the principle which, with lignine or 

 woody fibre, constitutes the vegetable cell, has hitherto been 

 considered as capable of resisting the action of all the digestive 

 fluids and other solvents ; so that the whole of the vegetable 

 substances which essentially consist of it have been held to 

 reappear unchanged in the excrements of herbivorous and 

 omnivorous animals. There is reason to think that, at least in 

 some animals, as in the beaver, celluline undergoes solution in 

 the lower part of the intestines, where the secretions acquire 

 an alkaline character. The effect of alkaline secretions on 

 celluline is probably to convert it into starch of which here- 

 after. 



Gum. Among the older authorities on dietetics and on 

 therapeutics gum was held an important article of food, and 

 also a valuable demulcent, even in those canals of the living 

 body to which fluid has access only by secretion from the blood. 

 Modern chemistry, in the mean time, contradicts this belief, 

 denying that gum can either directly enter the blood from the 

 alimentary canal, or that it is there convertible into any soluble 

 principle, by the change into which it might gain access to the 

 blood. Thus, if the present views of chemists rest on sure 

 grounds, the gum received into the stomach, notwithstanding 

 its great solubility, must almost wholly pass unchanged with 

 the excrement. 



Starch. Starch is by far the most important of the carbo- 

 hydrates under consideration. As already noticed (p. 65), starch 

 is acted on powerfully by the saliva and by the pancreatic juice. 

 It is now long since Magendie showed that, while neither 



