366 PROTOPLASMIC ACTION AND NERVOUS ACTION 



with alterations in this structure. In particular the fore- 

 going evidence indicates that the temporary breakdown 

 of the semi-permeable surface-lamella or limiting layer 

 of the protoplasmic emulsion influences profoundly the 

 chemical and other processes occurring in the cell 

 interior; apparently the effects of this surface-change 

 are transmitted throughout the whole mass of protoplasm, 

 and the physiological activities of the cell are changed 

 correspondingly. 



It has already been mentioned that experiments of a 

 kind closely analogous to those described for unfertilized 

 egg cells may be performed with irritable tissues like 

 muscle and nerve, both of which when immersed in 

 pure isotonic solutions of neutral sodium salts undergo 

 rhythmical or other stimulation, which may be checked 

 by calcium salts or anaesthetics; and the above-cited 

 experiments with Arenicola larvag afford other and more 

 direct evidence that stimulation and permeability- 

 increase are closely associated. Hober's experiments on 

 the influence of anaesthetics in checking the development 

 of the negative electrical variation produced in muscle 

 by application of KCl solution furnish evidence of a 

 similar kind. The effects of neutral salts may thus 

 be more or less completely antagonized by anaesthetics 

 as well as by the alkali earth cations. In all of these cases 

 prevention of permeability-increasing action runs parallel 

 with prevention of stimulation or of the normal manifes- 

 tations of stimulation.^ 



Conversely any strongly cytolytic action has a stimu- 

 lating effect. The larvae of Arenicola contract strongly in 

 solutions of cytolytic agents Uke chloroform; this effect 



^ Cf. chaps viii, ix. 



