LIPIDS PRESENT IN BRAIN AND NERVOUS TISSUE 763 



Table 17 



The Comparative Lipid Composition (in per Cent) of Human and of Bovine 



Medullated and Non-medullated Nerves, and of Different Peripheral Nerves 



of Human Subjects 



Compn. of lipid extract 

 of nerve on dry basis" 



Non- Medul- Compn. of normal human nerves* 



medullated lated ; 



(splenic, (ischial, Femoral Sciatic Post-tibial 



Substance bovine) human) (23 nerves) (3 nerves) (12 nerves) 



Water — 65. 8 e 68. C 68. 3 C 



Total extract 11.5 46 . 6 



Total phospholipids .. . 13. 36* 13.58 d 13.13 d 



Lecithin 9.8 29 — 



Cephalin 23.7 12.4 — — 



Cholesterol 47.0 25.0 4.37 d 4.59* 4.37 d 



Cerebrosides 6.0 18.2 5.36<* 4.52* 4.24 d 



Fat — 9.05 e 9.03 c 8.04 e 



• F. Falk, Biochem. Z., 13, 153-172 (1908). 



6 L. O. Randall, J. Biol. Chem., 125, 723-728 (1938). 



c Calculated on moist basis. 



d Calculated on dry basis. 



of the degeneration. Neutral fat decreased during the first four to eight 

 days, and returned to normal within thirty-two days. Little change was 

 noted in the free cholesterol, sphingomyelin, and cephalin content during 

 the first eight days, but a rapid decrease was noted in from eight to thirty- 

 two days. Cholesterol ester, which was absent from the normal nerve, 

 made an appearance and reached a maximum value after sixteen days. 

 It is suggested that some of the acids liberated by the other lipids may com- 

 bine with free cholesterol to form the ester, while others may be converted 

 into neutral fat. In a related series of tests, Burt and McNabb 326 noted 

 that a somewhat similar pattern was followed after the nerve was crushed 

 (but not cut). The wet weight of the nerve increased after the operation, 

 reaching the maximum at thirty-two days and returning to normal after 

 144 days. The total lipid decreased for the first sixteen days, remained 

 constant for from sixteen to forty-eight days, and then gradually increased. 

 However, after 144 days, the total lipid content was still less than it was in 

 control nerves. Neutral fat had returned to normal at the end of forty- 

 eight days, but the myelin lipids were present in the amount of only 44% 

 of their original content at the end of 144 days. May and Thillard 327 

 reported that the cerebroside content in the degenerated sciatic nerve of 

 the dog first increased to 69% during the three days following sciaticotomy, 



327 R. M. May and M. J. Thillard, Bull. soc. chim. biol, 35, 307-311 (1953). 



