PHYSIOLOGY OF CELL-DIVISION 375 



than in others before the plasma-membrane loses its normal 

 insulating and semi-permeable properties. This specific degree 

 of resistance is correlated in a remarkable manner with the 

 resistance to the cytolytic action of chemical agents like saponin. 

 Rywosch found, using a series of corpuscles from different mam- 

 mals, that there was an inverse relation between the resistance 

 to hypotonic NaCl solution and the resistance to saponin, i.e., 

 those corpuscles most resistant to hypotony were least resistant 

 to saponin.2'1 Since saponin appears to act by combining with 

 the cell lipoids, lecithin and cholesterol,^^ j^ would seem that 

 these differences depend on differences in the lipoid - content 

 of the plasma-membrane. The analyses of Abderhalden and 

 of Mayer and Schaeffer -^ indicate that the corpuscles least re- 

 sistant to hypotony are those richest in cholesterol. The pre- 

 ponderance of cholesterol over lecithin in corpuscles, as well 

 as in the artificial lipoid membranes of Pascucci,-'' seems to 

 impart a resistance to the disintegrative action of saponin, at 

 the same time rendering the cell less capable of resisting osmotic 

 distention. Variations in the lipoid-content of the egg at dif- 

 ferent periods may thus form the basis of the above variations 

 in the resistance to osmotic disruption. As indicating a possible 

 relationship of this kind, I have recently called attention" to 

 the interesting observation of Lyon and Schackell that the un- 

 fertilized Arbacia egg has a decidedly higher iodine-combining 

 power than the fertilized egg;-'' this suggests that at fertilization 

 there is a decrease in the iodine-combining constituents of the 

 plasma-membrane, e.g., cholesterol or other unsaturated lipoids. 

 It seems probable that similar variations may occur during the 



21 Rywosch, Arch. f. d. ges. Physiol., 1907, vol. 116, p. 229. 



22 Ransom, Deutsche med. Wochenschr., 1901, no. 13; Pascucci, Beitrage zur 

 chem. Physiol, u. Path., 1905, vol 6, p. 552; Hausmann, ibid., p. 567; K. Meyer, 

 ibid., 1908, vol. 11, p. 357; Windaus, Ber. d. deutsch. chem. Ges., 1909, vol. 42, 

 p. 238. 



23 Abderhalden, Zeitschr. f. physiol. Chem., 1898, vol. 25, p. 65; Mayer and 

 Schaeffer, Comptes rendus, 1912, vol. 155, p. 728. See also Kauders, Biochem. 

 Zeitschr., 1913, vol. 55, p. 96. 



24 Loc. cit. 



25 Amer. Journ. Physiol., 1916, vol. 40, p. 265. 



26 Lyon and Shackell, Science, N.S., 1910, vol. 32, p. 249. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 21, NO. 3 



