32 The Structure of Protoplasm 



marine ovum with a microdissection needle induced liquefaction. If 

 the egg was allowed to rest, it appeared to revert to its original 

 consistency. 



Marsland, and Brown and Marsland (see, for instance, 19) have 

 found that the application of high hydrostatic pressure inhibited cell 

 motion, cell division, and protoplasmic streaming. As these properties 

 diminished in extent with increasing pressure, there occurred a 

 steady diminution in the structural viscosity of the plasmagel por- 

 tion of the protoplasm, until, at high pressures, complete inhibition 

 of these activities was attained and the viscosity curve reached a 

 constant, low value. When the pressure was released, the cells 

 reverted to normal. Marsland concludes that these physiological 

 functions are linked to a reversible solation-gelation mechanism in 

 the cell. Apparently the plasmagel of Artioeha, Arhacia, and Elodea 

 cells shows structural viscosity as well as thixotropy.- From experi- 

 ments with microdissection, Seifriz (44) has concluded that the 

 consistency of protoplasm is not uniform but varies from species to 

 species and with physiological states. Both he and Northen (33, 34) 

 have presented evidence to show that protoplasm can have struc- 

 tural viscosity. Under these conditions, anomalous viscosity and 

 thixotropy are strong evidence for a labile, micellar framework. 



Elasticity. It is characteristic of many gels produced from rod- 

 shaped particles that they have rubber-like high reversible exten- 

 sibility, i. e., elastic properties. It was noticed by Freundlich and 

 Seifriz (12), for instance, that only those soap solutions which 

 contained rod-shaped aggregates were elastic. Gelatin (12, 14), 

 elastoidin (37) , elastin (21, 37) , and collagen (14, 37) , to name a 

 few proteins, can all be brought into an elastic state. These are 

 members of the fibrous or extended group. 



In addition, both Scarth (40) and Seifriz (43, 44) have found that 

 cytoplasm is elastic. For instance, Seifriz found that a nickel par- 

 ticle, which had been pulled through cytoplasm by a magnetic field, 

 tended to revert to its initial position when the field was removed. 

 Scarth has pointed out that cytoplasm can be elastic even while 

 streaming. It was also observed by Seifriz that red blood cells on 

 being stretched are highly elastic. Mudd and Mudd (31) have like- 

 wise observed a high reversible extensibility in normal leucocytes 

 engaged in phagocytosis. Part of these latter phenomena may have 

 been due to the membrane. 



As mentioned above, when rubber-like substances are stretched, 

 an extension of the molecular chains may take place without a change 



