DIGESTION OF THE CARBOHYDRATES 237 



blood is greatly increased above the normal, a condition which is known 

 as Lipemia. It is stated that in these cases the power of the blood to 

 render fats diffusible is diminished, the excess of fat being present 

 wholly in the emulsified, or non-diffusible condition. 



The Lecithins are very readily and rapidly split by lipase into fatty 

 acids and Glycerophosphoric Acid. This latter compound, however, is 

 not split by the digestive juices. It is not known whether hydrolysis 

 necessarily precedes the absorption of the lecithins. The rapidity 

 with which they are split by lipase indicates that at any rate a large 

 proportion of the lecithins must inevitably be hydrolyzed before 

 absorption can be completed. On the other hand the extreme solu- 

 bility of lecithins in solutions of bile-salts encourages the view that 

 a part at least of these substances may be absorbed without prelimi- 

 nary digestion, and this view is further supported by the remarkable 

 effects of egg-lecithin upon the growth and development of animals 

 and upon the nitrogenous balance, when it is administered by mouth, 

 effects which, as yet, have not proved possible to evoke by the adminis- 

 tration of the constituent parts into which it disintegrates upon 

 hydrolysis. It is, however, possible that these effects of administering 

 lecithin may be attributable, not to lecithin itself, but to impurities 

 which are commonly associated with crude preparations of lecithin. 



Cholesterol has been definitely shown to be absorbed as such. If 

 an abnormal quantity of cholesterol be administered by mouth to 

 animals, the excess is laid up in certain tissues, particularly those of 

 the liver, spleen and suprarenal gland, and serious lesions may result 

 from the accumulation of these deposits. Certain organs, e. g., the 

 kidneys, remain free from cholesterol deposits even when cholesterol is 

 administered in very great excess, but if lesions arise from some other 

 cause, for example if Nephritis is induced by the administration of 

 uranium salts, then cholesterol tends to become deposited in the 

 injured tissues. In rabbits, but, so far as has yet been ascertained, not 

 in other species of animals, the administration of excess of cholesterol 

 is followed by the formation of large deposits in the intima of the 

 arterial walls, particularly in the wall of the aorta, leading to the 

 formation of atheromatous lesions resembling those which are observed 

 in cases of Arteriosclerosis. 



The Cholesterol Esters, however, are not saponifiable by lipase and 

 are not absorbed. Hence Lanoline, administered by mouth, is recover- 

 able quantitatively in the feces. 



The Bile-salts, which serve as a vehicle and adjunct in the absorption 

 of the fats, undergo a partial circulation in the body, for after entering 

 the small intestine through the channel of the bile, they are partially 

 reabsorbed during their passage with the foodstuffs down the intestine. 

 Thus Glycocholic Acid is nearly absent from the bile of carnivora, but 

 on administering this bile-acid to carnivorous animals, it appears in 

 important quantities in their bile. 



