INORGANIC SALTS 165 



NaCl (or similar unbalanced solution of alkali salt; 

 the larvae contract strongly and the yellow pi^qnent 

 begins to diffuse from the cells; by degrees the cilia 

 cease movement and undergo a visible breakdown or 

 disintegration (suggesting liquefaction or absorption (jf 

 water). In a solution of NaCl containing a little 

 CaCla (95 volume m/2 NaCl plus 5 vols, m/2 CaCb) all 

 of these immediate effects are prevented, and the larva; 

 retain their normal appearance and behavior for some 

 time and die much more gradually.^ 



In this case it is clear that the iimnediate action of 

 the pure salt-solution is upon the surface structures — 

 cilia and plasma membranes — which quickly lose their 

 normal structural coherence and continuity; the result 

 of this change in the ciha is physical breakdown, and 

 in the plasma membrane a marked increase of permea- 

 bility, hence the diffusion of soluble cell-constituents to 

 the exterior and the progressive disorganization. In 

 many other organisms and cells it can also be shown that 

 an abnormal increase of permeability is produced by 

 pure solutions of Na salts and prevented by the addition 

 of CaCla or other antagonistic salt."^ The exj^eriments of 

 Osterhout on the electrical conductivity of Lamina ria 

 and other plant tissues afford perhaps the clearest evi- 

 dence that the toxic action of pure NaCl solutions is the 

 result of a destruction of semi-permeabiUty and that 

 antagonistic salts (CaCL and others) produce their anti- 



^ American Journal of Physiology, XXIV (1909), 14; cf. pages 22 iT. 



2 In an earlier paper {Biological Bulletin, XVII [igog], 188) I have 

 given a summary of observations showing tlie correlation between 

 permeability-increasing action and toxicity for compounds oUicr than 

 salts. 



