20 COMPARATIVE PHYSIOLOGY 



permeability of the muscle cell by its action on the colloidal 

 lipoid constituents of the surface layer. The work of Clowes 

 affords a crude model of how this effect might be produced. 

 In an oil-water emulsion addition of Ca salts produces a reversal 

 of phase so that the water becomes the internal and the oil the 

 continuous phase, i.e. so that the system as a whole becomes 

 impenetrable to water soluble substances. For a more realistic 

 conception the work of Neuerschloss on lecithin sols should 

 be consulted. If Ca determines the condition of the lipoid 

 constituents of the cell surfaces, the assumption that Na and K 

 are nomadic ions in Mines' sense provides for a ready explana- 

 tion of the widespread antagonism of Ca to Na as illustrated 

 by the work of Mines on striped muscle and that of Clark on the 

 vertebrate heart. Such antagonism might be regarded simply 

 as the opposition to the penetration of Na ions set up by surface 

 action of calcium. 



An example drawn from the field of invertebrate physiolog}^ 

 is afforded by the work of LiUie (1909) on the larvae of Areni- 

 cola. The larvae of this polychaete in isotonic solutions of the 

 chlorides of Na.,K., Li., and NH4 undergo contraction to about 

 half their normal length in a few seconds, and simultaneously 

 the yellow pigment enclosed in the cells of the organism 

 diffuses out into the medium, showing that the normal semi- 

 permeability of the cells has been suspended. Solutions of 

 the chlorides of Mg. . and Ca. . do not have this action either 

 as regards the contracture or discharge of colouring matter ; 

 and addition of a small quantity of Ca. . ions to a solution of 

 isotonic sodium chloride prevents the contracture and pigment 

 extrusion produced in a pure solution of the latter. On the 

 other hand lipoid-solvent anaesthetics such as chloroform 

 produce contracture and discharge even in pure magnesium 

 chloride. This antagonism is by no means confined to muscular 

 phenomena. Thus Loeb (19 12) showed that if eggs of the 

 Atlantic minnow (Fundulus) are placed in hypertonic sea- water 

 they remain alive for days, floating on the surface in an 

 apparently impermeable condition. If for sea- water hyper- 

 tonic NaCl is substituted, they sink to the bottom, undergo 

 shrinkage and rapidly perish. The addition of a small quantity 



