THE CHEMISTRY OF THE ANIMAL BODY. 559 



members of the glycose (sugar) series — i. e. substances which are characterized by the 

 presence of either aldehyde-alcohol, — CHOH — CHO, or ketone- alcohol, — CO — CH.< MI, 

 radicals. The constituents of glycerose, from the number of their carbon atoms, are 

 called trioses. On boiling glycerose with barium hydrate the twu constituents readily 

 unite to form i- fructose (levulose). 



Glycerin Phosphoric Acid, (HO) 2 C 3 H 5 .H 2 P0 4 .— This is the only ethe- 

 real phosphoric acid in the urine. It is luiind in mere traces. 



Lecithin, C 3H/ (C " H2U - A)2 



3 3 \O.PO.(OH).O.C 2 H 4 .N(CH 3 ) 3 OH.— Lecithin is found 



in every cell, animal or vegetable, and especially in the brain and nerves. 

 It is found in egg-yolk, in muscles, in blood-corpuscles, in lymph, pus-cells, 

 in bile, and in milk. On boiling lecithin with acids or alkalies, or through 

 putrefaction in the intestinal canal, it breaks up into its constituents, fatty 

 acids, glycerin phosphoric acid, and cholin (see p. 543), substances which the 

 intestine may absorb. The fatty acids may be stearic, palmitic, or oleic, two 

 molecules of different fatty acids sometimes uniting in one molecule of 

 lecithin : hence there are varieties of lecithins. Through further putrefaction 

 cholin breaks up into carbonic oxide, methane, and ammonia. 1 Lecithin 

 treated with distilled water swells, furnishing the reason for the " mvelin 

 forms" of nervous tissue. Lecithin is readily soluble in alcohol and ether. 

 It feels waxy to the touch. Protagon, which has been obtained especially 

 from the brain, is a crystalline body containing lecithin and cerebri)} — which 

 is a glucoside (a body separable into proteid and a sugar). The chemical 

 identity of protagon is shown in that ether and alcohol will not extract lecithin 

 from it. 2 Protagon readily breaks up into its constituents. While protagon 

 seems to be regarded as the principal form in which lecithin occurs in the 

 brain, simple lecithin is believed to be present in the nerves and other organs. 

 This subject has not been properly worked out. Noll 1 states that the 

 quantity of protagon in the spinal cord may amount to 2o per cent, of the 

 dry solids, in the brain to 22 per cent., and in the sciatic nerve to 7.5 per 

 cent. Regarding the synthesis of lecithin in the body, or the physiological 

 importance of the substance, absolutely nothing is known. 



Fat in the Body. — Animal and vegetable fats consisl principally of 

 a mixture of the triglycerides of palmitic, stearic, and oleic acids. In the 

 intestines the fat-splitting ferments convert a small portion offal into glycerin 

 and fatty acid ; the fatty acid unites with alkali to form a soap, in the presence 

 of which the fat breaks up into fine globules called an emulsion : the fat-split- 

 ting ferment then acts further on the fat, probably converting it all into tatty 

 acid and glycerin.' A line emulsion of lanolin ( fatty acid in combination with 

 cholesterin, isocholesterin, etc.) is not absorbed, because the intestine dues 

 not break up the combination/ and the melted particles themselves cannot 



1 JIasebroek: Zeitschrift fur physiologische Chemie, 1888, Bd. 12, 8. 1 18. 



2 Gamgee and Blankenhorn: Journal of Physiology, 1881, vol. ii. p. 113. 



* Zeitschrift fur physiologische Chemie, L899, Bd. 27, S. 370. 



* Frank, ( ). : Zeitschrift fur Biologic, 1898, Bd. 36, 8. :><>*. 

 6 Counstein : Archiv fur Physiologie, L899, S. 30. 



