I CYTOPLASM 185 



served is proved by the fact that it is able revert to the normal state 

 of swelling in which protoplasmic flow is resumed. In spite of its 

 magnitude, cap-plasmolysis must be designated as limited swelling, and 

 in the case of colloids with limited swelling we always have some sort 

 of meshwork. 



It is incumbent upon us to give the most careful consideration to 

 any objections of a physico-chemical nature, since these concern the 

 fundamentals of the postulated theory of junctions. According to 

 ScHULZ (1939), the Van der Waals cohesive forces are too small to 

 establish fixed bonds between molecules, so that a continual inter- 

 change of these junctions must be assumed. Considering the labile 

 nature of the invisible protoplasmic structures, it seems to me that 

 this should be valued as constructive rather than destructive criticism. 

 The decisive point is, that the cohesive forces between the macro- 

 molecules of the cytoplasm act as struct ure-Joijnmg elements, as is 

 clearly shown by the structure of mesophases (p. 51). Although long- 

 range forces are even smaller than the Van der Waals forces, to 

 which they are related, they must also be included among the possible 

 junctions, since they possess structure-forming faculties. According 

 to Bernal (1940) and Fankuchen (1941), they can cause macro- 

 molecules which are up to 1 50 A apart to form oriented gel structures! 



K. H. Meyer (1940 a, p. 607), on the contrary, regards the cohesive 

 bonds as true junctions. According to him, the distinction between 

 several different types of junctions goes too far; a division into 

 cohesive and valency bonds would amply suffice. Against this objection 

 it can be said that chain molecules with homopolar cohesive bonds 

 (e.g., waxes) or chiefly heteropolir cohesive bonds (e.g., cellulose) 

 show a fundamentally different behaviour in the physiological range 

 of temperatures. Whereas wax becomes plastic at 37° as a result of 

 the weakening of the homopolar cohesive bonds, a separation of the 

 polysaccharide chains in cellulose can only be brought, about by 

 suitable hydration of the heteropolar cohesive bonds. Admittedly, 

 homopolar cohesive bonds can also be solv^ated by lipophilic swelling 

 media (benzene, etc.). Under physiological conditions, however, 

 solvating media of this kind need not be considered, and it would 

 seem that the division suggested suits the purpose in the case of living 

 hydrogels. Similarly, the reaction to chemical interference (hydrolysis, 

 hydrogenation, etc.) of a gel frame containing only heteropolar 



