600 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



phospholipid exist in the liver, is not a new one, but was suggested earlier 

 by Artom et aL 355 and by Sinclair. 46 The latter investigator demonstrated 

 that the fatty acids in one portion of the liver phospholipids are readily re- 

 placed by elaidic acid, while the second portion is resistant to such a change. 

 MacLachlan et al. S5Z do not believe that the interchange of a- and ^-phos- 

 pholipids takes place physiologically, although they do not completely dis- 

 count this as a possibility. 



In contradistinction to the role of the a-lecithins and /3-cephalins as meta- 

 bolic phospholipids, the ^-lecithin, a-cephalin fraction must be regarded as 

 the true element constant. The hypothesis of Terroine and Belin 352 that 

 the phospholipid portion of the constant component consists only of the 

 lecithin type of phospholipids must be revised in the light of this more recent 

 work. 



Moreover, the question as to whether or not the quantity of the com- 

 ponents in the element constant is uniform is a much debated problem. In 

 his later review, Terroine, 351 cites the work of Alf Klem 356 on the uniformity 

 of the constant component in rats (fatty acids equaled 1.54 and 1.58% of 

 body weight), and of Valla 357 for the values in mice (2% of body weight). 

 The French investigator suggested that a more accurate index, from a bio- 

 metric point of view, for the constant component would be the ratio, at the 

 time of death, of the fatty acids in the entire organism to the total nitro- 

 gen. 



On the other hand, there is considerable evidence which is contrary to the 

 thesis that the level of phospholipids is a constant value. Thus, Boyd 358 

 has shown that the phospholipids in the leucocytes vary with the physio- 

 logic activity of the organism as a whole, or of a certain tissue. After an 

 operation, the phospholipids increase 200% if recovery ensues, or fall if 

 postoperative complications occur 358 ; a similar phenomenon obtains fol- 

 lowing fever. The phospholipids in the white corpuscles of women in- 

 crease for three weeks following parturition. 359 An increase in phospholipid 

 content occurs in the rabbit ovary during pregnancy, 360 which reaches a 

 maximum of 300% of the normal. However, this also returns to normal 

 before parturition. 360 It has been shown that, in such closely related or- 

 gans as the mammary glands, uterine mucosa, and the corpus luteum, the 



355 C. Artom, G. Sarzana, and E. Segre, Arch, intern, physiol, 47, 245-276 (1938). 



356 A. Klem, Norske Videnskaps-Akad., Oslo, Hvalradets Skrifter, No. 11, 49-108 

 (1935). 



357 S. Valla, Bull. soc. chim. biol, 17, 1715-1740 (1935). 



358 E. M. Boyd, Can. Med. Assoc. J., 31, 626-633 (1934). 

 369 E. M. Boyd, Surg. Gynecol. ObsteL, 59, 744-751 (1934). 

 360 E. M. Boyd, J. Biol. Chem., 108, 607-617 (1935). 



