ABSORPTION 



289 



they are taken up unaltered, probably by the lacteal vessels, 

 and excreted by the kidneys. This constitutes the temporary 

 glycosuria which sometimes follows a diet rich in carbohydrate. 

 The lacteal path of absorption is of interest, for, as we shall see 

 presently, physiologists have assigned the bloodvessels as the 

 path by which sugar is taken up. Nevertheless, years ago Colin 

 insisted that in the herbivora the chyle vessels took up sugar. 

 The chyle of a horse on an ordinary diet of hay and oats was 

 found by him to yield 13 to 16 per cent, sugar, and several such 

 observations are referred to by him in terms which lead one to 

 believe his experiments were adversely criticised by Bernard. 

 The physiologist of the present day regards the bloodvessels 

 of the villus as the path by which the sugar mainly gains entrance 

 to the body. From here it is carried to the portal vein, and 

 passes direct to the liver. We have seen (p. 246) that the sugar 

 percentage in the portal vessel may vary : 0-4 per cent, has been 

 found after a heavy carbohydrate meal in the dog, and 02 per 

 cent, in the same animal during starvation. On the other hand, 

 a definite percentage is maintained in the other vessels of the 

 body, and the cause of this has been fully considered elsewhere 

 (p. 249). 



The absorption of carbohydrate by the animals of the farm 

 has been the subject of considerable investigation. The ruminant 

 in all cases is better in this respect than the horse, as may be 

 seen from the following table : 



The practical application of these facts is very evident. All 

 the above foods in a given quantity are richer for the ruminant 

 than the horse. In dieting horses, according to the market 

 value of grain, it is well to ascertain what proportion of its 

 proximate principles are digested, or it may prove far from 

 economical. 



Absorption of Proteins. — Proteins, we have seen, are incapable 

 of absorption as such. Pepsin, trypsin, and erepsin convert 

 them into peptones and proteoses, and in this form, or when 

 still further broken down by trypsin and erepsin into amino- 

 bodies, they are taken up by the bloodvessels of the intestine. 



