TENSION PHENOMENA OF LIVING ELI- Ml. NTS. IK) 



Nathanson 1 supposed the plasma membrane to be a mosaic 

 of lipoids and "protoplasm," but it is evident that if the lipoid 

 portion is not continuous, it can not make the cell impermeable 

 to any -ubstance. 



( /apck- states that lipoid solvents cause cytolysis when the 

 surface tension of the solution is reduced to .68, and concludes 

 from tlii- that the plasma membrane contains glycerine tri-oleate 

 sinci ii- emulsion reduces the surface tension of water to thi> 

 figure. 



Tin- diffusion of water-soluble substances through swollen- 

 ]il.n _els" or "sols" of gelatine, varies inversely with the 



viscosity (Arrhenius). The great hysteresis of gelatine gels i- 

 t.il.en advantage of to show that diffusion depends on tin vis- 

 cositj ami not on the per cent, of gelatine, at the same temper- 

 aim 



Tin absorption of water by a gelatine plate increases its per- 

 meability. and the temperature and therefore the presence of 

 MI! .-tain es which affect this swelling of gelatine affect its perme- 

 abilit\. Impregnation of colloidal membranes \viih bile salts, 

 al-oliol, ether, acetone or sugar changes (usually increases) 

 tin ir | .ei mt -ability. The effects of substances on tin- rate of 

 dilliisioii through gelatine plates, and on their swelling (viscositj 

 and tin -It ing point arc not always quite parallel. 4 



In the substance added to the membrane is removable, 



(he i lian^c in permeability becomes reversible, which is true 

 in regard to many of the substances mentioned above. Changes 

 in non-li\in- membranes are usually only partially reversible or 

 are irreversible. I >enaturalization of a colloid membrane by 

 lu-ai. heavy metals, or other coagulative agents which induce 

 chemical changes in the membrane, or the addition ot substances 

 which cannot be removed, produce irn -\vr-ible changes in 

 permeability. 



That the permeability of the membrane- in living ti--ne is 

 increased at death is proven by a host of observation-. The 

 electric conductivity increases enormously at death. Contained 



Jahrb , i r. Bot., 1903, XXXVIII.. 284; 190). XXX IV.. 601, and XI... 403- 

 /-'.-. deut ill. hot. Gesell., 1910. 28, 480. 



r. Asher & Spiro's Ergeb. der Physiol.. 1908, VII., 99- 

 . loc. cit. 



