INORGANIC SALTS 185 



insolubility, and impermeability to water-soluble sub- 

 stances (like sugar and salts), require the presence of 

 Ca compounds. These compounds impart the necessary 

 structural stability to the whole protoplasmic complex. 

 A fact of interest in relation to this question is Meigs's 

 recent observation that an approach to semi-permeability 

 can be imparted to certain artificial colloidal membranes, 

 otherwise highly permeable, by depositing insoluble Ca 

 salts (phosphate) in their substance.^ 



These facts and considerations are consistent with 

 the view that Ca compounds, e.g., Ca soaps, play a 

 similar part in the surface layers of protoplasm, and the 

 recent interesting experiments of Clark^ with the frog's 

 heart lend support to this general conception. He finds 

 that the heart, after being weakened by prolonged 

 perfusion with Ringer's solution, rapidly regains its 

 vigor if perfused with Ringer's solution to which serum, 

 serum-Hpoids, lecithin, or soaps of higher fatty acids, 

 have been added. During perfusion with pure Ringer's 

 solution the heart loses to the solution some material 

 which has a similar reviving action when perfused 

 through other exhausted hearts. In order that these 

 substances, or soap, should exhibit this beneficial action, 

 calcium must be present. He concludes that the benefi- 

 cial action of the soaps is associated. with the adsorption 

 of a water-soluble Ca soap or similar compound upon the 

 surface of the muscle cells, and puts forward the hypothe- 

 sis ''that the activity of the heart is dependent upon the 

 semi-permeabihty of the cell to electrolytes, that this is 



^ Meigs, American Journal of Physiology, XXXVIII (1915), 456. 



* A. J. Clark, Journal of Physiology, XL VII (1913), 66; also Clark 

 and Daly, ihid., LIV (1921), 367. 



