MOTOR RESPONSES 343 



tested (thirty-one), except (NH,)oSO, and NH.CaHgO,, induce rever- 

 sal; but that none of the bivalent and trivalent cation salts tested (nine- 

 teen), except CaHPO, and MgHPO,, induce it. Also that Ba(OH)2, 

 H3PO4 and HXoO^ induce reversal, while HCL and lactose do not. 



These authors contend that the duration of reversed action is closely 

 correlated with the concentration of the salts; that it varies with the kind 

 of salt at any given concentration; and that bivalent and trivalent cation 

 salts neutralize the effect of monovalent salts. 



Concerning the physiological processes involved in reversal in ciliary 

 action, they make the following statement: 



Copeland (1919, 1922) and Grave and Schmitt (1925) demonstrated 

 that the cilia in higher forms are closely connected with nerve fibers and that 

 their action is in all probability controlled by nerve impulses. The results 

 obtained in the investigations of Yocum (1918), Taylor (1920), Rees 

 (1922), Visscher (1927) and others on the neuromotor apparatus in the 

 protozoa, indicate that the action of the cilia in these forms is similarly con- 

 trolled. If this is true, the question arises as to how environmental changes 

 which have been observed to induce reversal in ciliary action influence 

 the neuromotor apparatus. This may be conceived to be either through 

 chemical changes produced in the receptors or elsewhere in the organism 

 or through changes produced in the electric potential at the surface, or in 

 the permeability and the consistency of the surface layer. . . . 



The results obtained by Mast and Nadler indicate that reversal in ciliary 

 action is largely dependent upon the cations, that it is induced by monovalent 

 but usually not by bi- and tri-valent cation salts, and that it depends upon the 

 concentration of the salts. . . . 



It is well known that adsorption of the cations is usually relatively greater 

 in bi- and tri-valent than in monovalent cation salt solutions and that the 

 adsorption varies with the concentration of the salts in the solution. This 

 seems to indicate that the difference in the action of the monovalent and 

 the bi- and tri-valent cation salts and the difference in the action of different 

 concentrations of the monovalent cation salts is at least in part associated 

 with differential adsorption of the ions in the various solutions, resulting 

 in changes in the electrical potential at the surface of the paramecia, which 

 directly or indirectly produce impulses in the neuromotor apparatus which 

 pass to the cilia and influence their action. The facts, however, that Ba(OH)2 

 produces reversal while BaCl^, CaCl,, MgCL do not, that H^QO^ and 

 H3PO4 produce reversal while HCl does not, that CaHPO^ and MgHPO^ 

 produce reversal while Ca3(PO_j)2 and Mg(POJo do not, all indicate 

 that there must be other factors involved in reversal aside from differential 

 adsorption of the cations. 



