Protoplasmic Streaming — Relation to Gel Structure 157 



example, differences in the metabolic reactions which are precursory 

 to the development of the mechanical energy. 



VI. SUMMARY OF CONCLUSIONS 



(1) The general effect of hydrostatic compression upon a num- 

 ber of different cells is to induce a uniform solation of gelated parts 

 (the plasmagel system) of the protoplasm. Each increment of 1,000 

 Ibs./in.- reduces the gel rigidity by almost 25 per cent. 



(2) All of the protoplasmic gels which have been studied appear 

 to conform to the type (Freundlich, '37) in which the process of 

 gelation is accompanied by a small increase of volume. 



(3) Certain types of cellular movement (amoeboid movement, 

 cyclosis, cell division, and the flow of pigment in unicellular pig- 

 mentary effectors) , in which protoplasmic streaming is the common 

 attribute, are especially susceptible to a pressure-induced inhibition. 

 In contrast, other physiological activities (muscular contraction, 

 nervous conduction, and the motility of cilia and flagella) are 

 augmented by low and moderate degrees of pressure and suffer 

 depression only in the higher range (above 5,000 Ibs./in.-) . 



(4) The inhibiting effect of pressure upon the various kinds of 

 protoplasmic streaming is in proportion to the degree of solation 

 which the pressure induces in the plasmagel systems. 



(5) To interpret these results, it is postulated that sol ^ gel 

 reactions constitute an intermediary mechanism whereby potential 

 energy is converted by the cell into mechanical energy — the mechani- 

 cal energy of the streaming protoplasm. 



FOOTNOTES 



'Brown ('34c), Marsland ('38 and '39), Pease and Marsland ('39). 



"Brown and Marsland ("36). 



'Kitching and Pease ('39). 



'Ebbecke ('36). 



° Marsland ('39b). 



'Pease ('40b). 



' Judging from the compressibility of muscle tissue (see Cattell, '36, p. 458) , 

 the loss of protoplasmic volume in the range of pressure used in the present 

 experiments, would be about 2 per cent. 



' Previous microscope-pressure chambers permitted observation of the com- 

 pressed specimens, but at much lower magnification (see, for example. Draper 

 and Edwards, '32) . 



" Leitz, U. M. 



'" This amount of working distance is necessary since the walls of the cham- 

 ber must be thick enough to support the high internal pressure. 



