656 ABSORPTION. 



b. Absorption of Drinks. 



It has been stated, that a wide distinction exists between the gastric 

 and intestinal operations that are necessary in the case of solid and 

 liquid food. Whilst the former is converted into chyme and passes into 

 the small intestine, to have its chylous part separated from it; the latter 

 is usually absorbed from the stomach or small intestine. 



The chyliferous vessels, we have seen, are agents and exclusive agents 

 of the absorption of chyle the nutritive product from the digestion of 

 solids. What, then, are the agents of the absorption of liquids ? There 

 are but two sets of vessels on which we can rest for a moment. These 

 are the lacteals or lymphatics of the digestive tube; and the veins of 

 the same canal. But, it has been seen, the chyliferous vessels refuse 

 the admission of everything but chyle. It would necessarily follow, 

 then, that the absorption of liquids must be a function of the veins. 

 Such is the conclusion of most physiologists, and on inferences that are 

 logical. The view is not, however, universally admitted; some assign- 

 ing the function exclusively to the lacteals; others sharing it between 

 them and the veins. Let us inquire into the facts and arguments ad- 

 duced in support of these different opinions. The advocates for the 

 exclusive agency of the chyliferous vessels affirm, First, That whatever 

 is the vascular system, that effects the absorption of drinks, it must com- 

 municate freely with the cavity of the intestine; and that the chyliferous 

 vessels do this. Secondly, That this system of vessels is the agent of 

 chylous absorption: a presumption, that it is likewise the agent of the 

 absorption of drinks. Thirdly, That every physiologist, who has ex- 

 amined the chyle, has described its consistence to be in an inverse ratio 

 with the quantity of drink taken; and, lastly, that when coloured and 

 odorous substances have passed into the intestine, they have been found 

 in the chyliferous vessels and not in the mesenteric veins. The experi- 

 ments, adduced in favour of this last position are, however, so few and 

 inadequate, that it is surprising they could have, for a time, so com- 

 pletely overturned the old theory. This effect was greatly aided by the 

 zeal and ability of the Hunters, and of the Windmill Street School in 

 general, who were the great improvers of our knowledge regarding the 

 anatomy of the lymphatic system. John Hunter, 1 who was one of the 

 first that positively denied absorption by the veins, and maintained that of 

 the lymphatics, instituted the following ingenious and imposing experi- 

 ment. He opened the abdomen of a living dog; laid hold of a portion 

 of intestine, and pressed out the matters it contained with his hand. 

 He then injected warm milk into it, which he retained by means of liga- 

 tures. The veins, belonging to the portion of intestine, were emptied 

 of their blood by puncturing their trunks; and were prevented from 

 receiving fresh blood, by the application of ligatures to the correspond- 

 ing arteries. The intestine was returned into the cavity of the abdo- 

 men ; and, in the course of half an hour, was again withdrawn and 

 scrupulously examined; the veins were still found empty, whilst the 



1 Observations on certain parts of the Animal Economy, by John Hunter, F. R. S., with 

 notes by Richard Owen, F.R.S., Bell's Library edit., p. 307, Philad., 1840. 



