366 ABSORPTION. 



Nasse's analyses, the solid matter of a given quantity of 

 blood could not be replaced out of less than three or four 

 times the quantity of lymph and chyle. 



Absorption ly the Lacteal Vessels. 



During the passage of the chyme along the whole tract 

 of the intestinal canal, its completely digested parts are 

 absorbed by the blood-vessels and lacteals distributed in 

 the mucous membrane. The blood-vessels appear to 

 absorb none but the dissolved portions of the food, and 

 these, including especially the albuminous and saccharine, 

 they imbibe without choice ; whatever can mix with the 

 blood passes into the vessels, as will be presently described. 

 But the lacteals appear to absorb only certain constituents 

 of the food, including particularly the fatty portions. The 

 absorption by both sets of vessels is carried on most 

 actively, but not exclusively, in the villi of the small intes- 

 tine ; for in these minute processes, both the capillary 

 blood-vessels and the lacteals are brought almost into 

 contact with the intestinal contents. 



It has been already stated that the villi of the small 

 intestine (figs. 80 and 81) are minute vascular processes 

 of mucous membrane, each containing a delicate net- 

 work of blood-vessels and one or more lacteals, and are 

 invested by a sheath of cylindrical epithelium. In the 

 interspaces of the mucous membrane between the villi, as 

 well as over all the rest of the intestinal canal, the lacteals 

 and blood-vessels are also densely distributed in a close net- 

 work, the lacteals, however, being more sparingly supplied 

 to the large than to the small intestine. 



It has long been, and is still, very difficult to explain 

 how absorption by the lacteals is effected. Various theories 

 on the subject have been promulgated, but there is still 

 much doubt whether any correct interpretation has yet 

 been suggested. Probably the cause of the confusion in 



