THE PHOSPHOLIPINS OR PHOSPHATIDS 115 



The majority of the phospholipins are rapidly hydrolyzed by the 

 fat-splitting ferments or Lipases, yielding fatty acids, glycero-phosphoric 

 acid and nitrogenous bases. Glycero-phosphoric acid is not split by 

 lipase, but is readily decomposed by dilute acids yielding phosphoric 

 acid and glycerol. Since glycero-phosphoric acid is not liberated from 

 phospholipins until they reach the small intestine, where the reaction 

 is alkaline, it would appear unlikely that it is split before absorption. 

 According to some authors, an enzyme exists in tissue extracts from 

 the liver, kidneys and intestinal mucosa, which is capable of bringing 

 about the decomposition of glycero-phosphoric acid, but the constant 

 presence of undecomposed glycero-phosphoric acid in small amounts 

 in normal urine would appear to render this doubtful. Optically in- 

 active glycero-phosphoric acid is readily prepared synthetically from 

 glycerol, and phosphoric acid; the glycero-phosphoric acid yielded 

 by hydrolysis of phospholipins is, however, levorotatory. It is soluble 

 in water and insoluble in alcohol. The calcium salt is readily soluble 

 in cold, but almost insoluble in boiling water. 



The Lecithins, the composition and probable structure of which, 

 have already been discussed, occur in all plant and animal cells. A 

 lecithin or a mixture of lecithins, is particularly abundant in the yolks 

 of eggs, and may be obtained in impure condition by extracting the 

 broken yolks with ether, and adding acetone to the extract. Lecithins 

 are particularly abundant in young and rapidly growing or embryonic 

 tissues. They progressively diminish as development proceeds and, 

 in the embryos of sea-urchins at all events, they are probably the 

 source from which the phosphoric acid is obtained which is required to 

 build up the nucleic acids in the nuclei of the new cells. The lecithins 

 are soluble in alcohol, ether, chloroform, carbon bisulphide, benzol, 

 and fats or fatty oils; they are precipitated from ether by the addition 

 of acetone. In water they swell up and form pasty masses which throw 

 out oily drops and threads, the so-called "myelin forms," into the body 

 of the liquid. This probably represents the beginning of an imperfect 

 emulsification, and the addition of soaps, saponins or bile-salts acceler- 

 ates and completes the process with the formation of relatively stable 

 milky emulsions which are coagulated by the addition of small quanti- 

 ties of salts of the alkaline earths (calcium, barium or strontium). 

 The lecithins have a peculiar greasy odor which is rather sharp and 

 reminiscent of dried brain-tissue. They are tasteless. 



It was formerly believed that lecithins stood in a peculiar relation- 

 ship to certain types of snake-venom and other hemolyzing poisons. 

 If a pure hemolyzing snake-venom be allowed to act upon thoroughly 

 washed blood-corpuscles, no hemolysis occurs. Upon the addition of 

 blood-serum or of impure lecithin, which by themselves are of course 

 without action, hemolysis ensues at once. It has been ascertained 

 by Bang, however, that pure lecithin prepared from yolk of eggs is 

 devoid of activating influence upon cobra -venom. It would thus 

 appear probable that the activating action of other preparations of 



