338 MOTOR RESPONSES 



Table 2 : Rate of Locomotion of A. Proteus in Sodium and 

 Calcium Salt Solution* 



Composition of the solution used to ascertain the effect of hydrogen-ion concentration 

 on rate of locomotion and gel/sol ratio in a balanced salt solution. To obtain different 

 hydrogen-ion concentrations, the acid and the alkaline components were mixed in dif- 

 ferent proportions. 



Note that the concentration of Na, K, Ca, and Mg remains constant, no matter what 

 the proportion of the two components is. 



In the second series of experiments the concentration of all the salts was increased 

 five times (after Pitts and Mast, 1933). 



Acid Component 



Alkaline Component 



Molar Ratio 



NaH2P04 0.00150N 



KH2PO4 o.oooioN 



CaH4(P04)2 O.oooioN 



MgCl2 0.00005N 



NaOH 0.00 1 50N 



KOH O.oooioN 



Ca(OH)2 o . 000 1 oN 



MgCU 0.00005N 



Na 60 



K 4 



Ca 2 



Mg I 



* After Pitts and Mast, 1933, by permission of the Journal of Cellular and Comparative Physiology, 

 Wistar Institute of Anatomy and Biology. 



Mechanics of response. — Concerning the action of chemicals produc- 

 ing these responses on Amoeba, Pitts and Mast make the following state- 

 ments : 



It is obvious that a substance in the environment may influence processes 

 which occur in a cell either by entering the cell and acting directly on 

 substances in the cell, or by acting on the surface of the cell in such a way 

 as to retard or facilitate the passage into or out of the cell of other sub- 

 stances which, owing to their presence or absence, induce alterations in 

 internal processes. . . . 



It may be assumed, then, either (1) that the gel/sol ratio depends upon 

 the entrance of salts into the cell and reaction between these and internal 

 substances, and that the rate of entrance of salts varies with the hydrogen 

 ion concentration; or (2) that the gel/sol ratio varies with the rate of en- 

 trance of hydrogen and hydroxyl ions into the cells and reaction between 

 these and internal substances, and that the rate of entrance of these ions 

 varies with the concentration of the salts and the hydrogen ions; or (3) that 

 the gel/sol ratio depends upon the exit of substances from the cell, e.g., 

 water, and that this depends upon the hydrogen ion concentration, and the 

 salt concentration and the kinds of salts present. Let us now attempt to 

 ascertain if the processes in question are in accord with any of these groups 

 of assumptions. . . . 



If they are in accord with the first of these assumptions, the gel/soI 

 ratio must vary directly or indirectly with the amount of salt that enters the 

 cell and this must vary directly or indirectly with the hydrogen ion con- 



