64 PHYSIOLOGY FOR NURSES 



tinal villi. This is proved by tying the thoracic duct so 

 the fluid it carries can not get into the blood. Animals 

 thus treated continue to absorb and utilize proteins as 

 before. The actual form in which nitrogenous foods 

 enter the blood current is that of the ammo acids, which 

 are carried to the various tissues which, in turn, select 

 such acids as are suitable for their repair or upbuilding. 

 Some of the organs, notably the liver, have the power 

 of converting these acids not into tissue but into some 

 other nitrogenous compound urea in the case of the 

 liver. 



If the contents of the small intestine be examined at 

 the ileocecal valve, it will be found that from 97 to 99 

 per cent of such foods as milk, eggs and meats have been 

 absorbed, while the proportion of vegetable protein 

 absorbed is much smaller from 70 to 80 per cent. This 

 seems due to the entanglement of the vegetable pro- 

 teins in indigestible cellulose. 



Absorption of Carbohydrates. Starchy food is ab- 

 sorbed as simple sugars. Rather more than a pound 

 (500 grams) may be utilized in a day, all, in the form 

 of dextrose, is stored up as glycogen, keeping the 

 amount of sugar in the blood constant about 15 per cent. 

 When excessive amounts of starchy food or sugar are 

 eaten, the liver may be, for the time, overworked and 

 sugar may temporarily appear in the urine. 



Absorption of Fats. The fatty acids and glycerin of 

 intestinal digestion are absorbed as such and appear, 

 to some extent at any rate, to be recombined in the 

 epithelial cells of the villi. After passing the epithelium 

 the fat is taken up by the lacteals of the villi and carried 

 by the thoracic duct to the beginning of the left in- 

 nominate vein where it is poured into the blood stream. 

 A small amount, however, appears to be absorbed directly 



