134 



The Structure of Protoplasm 



protoplasm. The greatest resistance to such displacement occurs in 

 the peripheral protoplasm, that is to say, in the plasmagel rather 

 than in the plasmasol. At 7,000 X gravity the displacement of the 

 formed elements of the sol region is practically instantaneous (Heil- 



brunn, '29) . Consequently, 

 it may be said that the so- 

 lation measurements ob- 

 tained deal entirely with 

 the gel portion of the 

 protoplasm of this cell. 

 (4) Equilibration to lower 

 pressures, steadily main- 

 tained 



In view of the marked 

 effects of the sudden high 

 compression of the Amoe- 

 bae, it seemed important 

 to ascertain the character- 

 istic form and movement 

 of the specimens when 

 equilibrated to lower pres- 

 sures which do not induce 

 such a drastic liquefaction 

 of the plasmagel. In the 

 experiments the amoebae 

 were exposed to the de- 

 sired pressure until the 

 characteristic form was 

 assumed, a matter usually 

 of about 5 minutes. In 

 most instances the same group of animals was compressed at suc- 

 cessively higher pressures and then decompressed, step-wise, through 

 the same pressure range, sufficient time for equilibration being 

 allowed at each pressure. 



The variation in form of the Amoebae as a function of pressure 

 involves a progressive diminution in the diameter of the pseudo- 

 podia which are formed. At lower pressures, i. e., up to 2,000 Ibs./in.,- 

 there is also a lengthening^'' of the pseudopodia, but thereafter both 

 the length and the diameter are reduced more and more. At 5,000 

 lbs. the pseudopodia, although numerous, appear as mere pin points 

 projecting from the surface of the otherwise spherical cell. Above 



Fig. 3. The solation effect of pressure in 

 the Amoeba. Specimens E (experimental) and 

 C (control) were centrifuged simultaneously 

 for only 10 seconds. E was in the pressure 

 section of the centrifuge at 8,000 lbs./in.% 

 whereas C was at atmospheric pressure. The 

 much greater fluidity of the plasmagel of E 

 is indicated by the sharp centrifugal zoning. 

 An equivalent zoning of atmospheric speci- 

 mens requires more than 3 minutes of cen- 

 trifuging. Note also in E, that the contractile 

 vacuole was on the point of being thrown 

 out from the centripetal end of the cell at 

 the instant when the nucleus reached the 

 opposite end: o, the oil zone; h, the hyaline 

 zone; g, the granular zone. 



