i86 PROTOPLASMIC ACTION AND NERVOUS ACTION 



dependent on the presence of Ca and lipoids at the 

 surface of the cells, and that during perfusion the heart 

 loses Hpoids and becomes more permeable to electro- 

 lytes." This conception of semi-permeability as depend- 

 ent on the presence of lipoids, and of the state of the 

 Hpoids as determined by the salts of the medium, is in 

 harmony with much recent work.^ It also affords a 

 point of view from which it is possible to understand 

 why the physiological effects of salts and of lipoid- 

 solvent compounds should have so much in common. 



^Blackman, "The Plasmatic Membrane and Its Organization," 

 New Phytologist, XI (191 2), 180; Clowes, loc. cit; Czapek, Oberfldchen- 

 spannung der Plasmahaut, Jena (1911); McDougall, Science, LV (1922), 

 653; Hansteen-Cranner, loc cit. See also Stiles's review of the subject 

 of cell permeability in New Phytologist, XX, XXI, XXII (1921-23). 



