ABSORPTION 175 



tose will be split and utilized at least in part, as the blood con- 

 tains a maltase. Blood appears to contain little or no lactase 

 or invertase, however, so that lactose or cane sugar which get 

 into the blood are excreted into the duodenum, or in the urine. 



Absorption of Fats. Fats are absorbed mainly in the form 

 of fatty acids and soaps. These are recombined with glycerine 

 in the cells of the intestinal wall, and pass into the lacteals as 

 neutral fat. 



In the absorption of fats the bile plays an important role. 

 If bile is excluded from the intestine, the absorption of fats is 

 greatly diminished. Large amounts of fatty acids, soaps, and 

 some fat appear in the feces, indicating that the fatty acids 

 and soaps are absorbed very slightly in the absence of bile. 

 Bile aids in the absorption process by its power of dissolving 

 fatty acids and soaps. These soaps and fatty acids dissolved by 

 the bile salts pass into the cells of the intestinal wall. Glycerine 

 also is absorbed, and from this and the fatty acids, neutral fat 

 is constructed. This passes for the most part into the lacteals, 

 thence along the lymphatics and into the thoracic duct whence 

 it is poured into the blood stream at the junction of the jugular 

 and subclavian veins. The bile salts which have entered the 

 blood with the fatty acids are picked out of the blood by the 

 liver and returned to the bile. 



During digestion, white corpuscles are known to gather in 

 large numbers in the neighborhood of the intestine. Evidently 

 they are concerned in some way in taking care of the absorbed 

 foodstuffs, but their role is as yet a matter of uncertainty. 



Most of the absorption of digestive products takes place in the 

 small intestine, so that little useful material is left by the time 

 the digested food reaches the large intestine. In this region, 

 however, there is a large absorption of water so that this valu- 

 able liquid is not wasted by excretion with the feces. 



