Chapter III — 15 — Physical Properties 



(Chodat and Boubier, Lepeschkin). Furthermore, certain ex- 

 periments are difficult to reconcile with the existence of such a 

 membrane. It has been known for a long time that when a filament 

 of Vaucheria is injured in such a way that the torn cellulose wall 

 allows portions of cytoplasm to run out, those coming in contact 

 with water immediately assume spherical form (Fig. 7). They 

 are seen at the same time to become enveloped in a delicate mem- 

 brane separating them from the surrounding substance. 



The microdissection experiments of Chambers on animal cells 

 have demonstrated that the cytoplasm always shows at its periph- 

 ery a more refractive zone, resulting from a condensation of its 

 substance, constituting a sort of membrane. When trying to insert 

 a microneedle in a living cell, it is noticed that, if the pressure is 

 not too great, there is formed a depression in the cytoplasm at the 

 point of contact as if an elastic membrane separated it from the 

 instrument. But this membrane does not have an autonomous exist- 

 ence. If it is destroyed over a small area, a membrane immediately 

 separates by condensation from the cytoplasm at the wounded spot. 

 By this same method, Seifriz has demonstrated at the periphery 

 of the Plasmodium of the Myxomycetes a very elastic membrane, 

 capable of stretching and contracting with the greatest ease, and 

 resistant to a remarkable degree, in short, a limiting layer of more 

 dense cytoplasm. Whenever it is torn, a new one forms immedi- 

 ately, as long as the cytoplasm is alive, whether the surrounding 

 substance be air or water. The same phenomenon is observed 

 in pollen tubes. If the tube is torn, it is seen that the cytoplasmic 

 masses which are detached from it are surrounded forthwith by a 

 membrane. From these experiments it can be concluded that each 

 fragment of naked cytoplasm possesses the property of separating 

 itself immediately, by a delicate membrane, from the substance 

 surrounding it. It is comprehensible that the cytoplasm may be 

 finely divided, being at all times surrounded by a delicate mem- 

 brane, as, for example, in the Plasmodium of Badhamia which 

 passed through the cotton wad. It seems demonstrated, further- 

 more, that this membrane is not, as was first thought, a differenti- 

 ated membrane of special constitution, but a limiting surface, a 

 sort of physical membrane, brought about by a condensation of the 

 cytoplasm in its zone of contact with the surrounding environment. 



The manner in which this membrane is formed can be com- 

 pared with the well known fact that in a complex liquid all mole- 

 cules capable of lowering the surface tension accumulate in the 

 peripheral layer. Now, proteins lowering surface tension and con- 

 centrating at the surface of their aqueous solution constitute vis- 

 cous films which reform immediately when torn. It even happens 

 that this concentration at the surface exceeds the maximum solu- 

 bility of the body in question. It then becomes flocculent and may 

 form a solid surface layer quite comparable to the ectoplasmic 

 membrane. 



Certain theoretical considerations, necessary to explain the 

 rapid penetration into the cell of certain substances, brought Over- 



