ABSORPTION. 



61 



FIG. 13. 



What becomes of the food absorbed by the blood-vessels ? 



It is taken by the portal vein to the liver, and there further 

 elaborated for tissue-nutrition. 



What becomes of the food absorbed by the lacteals ? 



It is collected from all the lymph-spaces in the villi and about the 

 glandular structure of the intestines, and is taken thence into the 

 larger lacteals, whence it passes through the mesenteric lymphatic 

 glands and into the receptaculum chyli of the thoracic duct (Fig. 13). 

 Hence it passes on into the blood-vas- 

 cular system, which it joins at the root 

 of the neck at the union of the left in- 

 ternal jugular and subclavian veins. 



Does chyle undergo change in the 



lacteals ? 



Yes. Peptones, as such, are not 

 found in the blood nor in the thoracic 

 duct, and in the same way sugar is 

 not more abundant in chyle after 

 absorption than in the blood ; nor 

 can we fully account for the fats 

 which are absorbed. The trace is 

 lost, to a great degree, after absorp- 

 tion of most substances, and we do 

 not know the exact history of the 

 metamorphoses which render them 

 tit for tissue-building. 



What elements are chiefly taken 



up by the portal system ? 

 All elements to a greater or less 

 degree, but the crystallizable sub- 

 stances are taken up in greater pro- 

 portion by the blood-vessels than by 

 the lacteals. Thus we find that 

 sugars and salts seem to pass into 

 the portal system, and the proteids 



and fats into the lacteal system in a Lacteals and Lymphatics during Di- 

 ... . gestion. 



little greater proportion. 



What is the appearance of chyle in the lacteals? 



It is opaque, whitish, milky from the minute fat-globules which 



