BIBLIOGRAPHY 209 



solution can render cells nearly impermeable to all ions, and that any- 

 excess of calcium over its normal sea-water concentration (Table V-ll) 

 tends to decrease the permeability of the cell. 



If the calcium salts react chemically with the mobile external surface 

 molecules in the presence of fatty acid molecules to form a calcium soap, 

 the surface becomes more polarized for the soap molecules are more 

 soluble in water than the original fatty acid molecules. The molecular 

 structure may then be pictured as more closely packed and the openings 

 of the mosaic pattern so reduced in area as to exclude the possibility of 

 infiltration of most solute molecules. 



A further important matter must be taken into consideration in setting 

 up a hypothetical model of a semi-permeable dynamic cell wall, namely, 

 the selective accumulative property of certain cells. This may be appre- 

 ciated after examining the data of Table V-ll. Of interest is the 

 analysis of the cell sap of Valonia macrophysa by Osterhout [1936], 

 which shows an unusually high potassium content as compared with sea 

 water. Note also the amount of potassium in red corpuscles as com- 

 pared with their plasma environment. It is difficult to explain these 

 results since there can be no apparent differentiation by the membrane 

 between sodium and potassium ions on the basis of their dimensions, 

 mobility, or electric charge. Jacques' recent work on the nature of the 

 protoplasmic surface of the cell in the marine plants Valonia and Halicys- 

 tis and in the fresh-water Nitella indicates that the cell membranes are 

 composed of non-aqueous layers at the inner and outer surfaces of the 

 protoplasm which possess different solubilities for various salts, potas- 

 sium being absorbed more rapidly than sodium in Valonia. 



In any case the structure and the structural changes that account for 

 the normal semi-permeability of the wall of the living cell (Rideal 

 [1939]) await final analysis* and must remain matters of speculation 

 until the biochemist and the biophysicist can furnish the necessary infor- 

 mation about the chemical composition and electrical properties of 

 plasma membranes. 



BIBLIOGRAPHY 



1888 de Vries, Hugo, Z. physik. Chem., 2, 415. 



1896 Starling, E. H., J. Physiol, 19, 312, and 24, 317 (1899). 



1903 Guye, P. A., and F. L. Perrot, Bull. univ. arch. sci. phys. nat., 15, 132. Also 



H. E. Edgerton and K. J. Germeshausen [1934]. 



1907 Morse, H. N., J. C. W. Frazer, and B. F. Lovelace, Am. Chem. J., 37, 324. 



1917 Macallum, A. B., Trans. Coll. Physicians Phila., 39, 289. 



1919 du Nouy, P. L., /. Gen. Physiol, 1, 521. 



* For a comprehensive discussion of the properties and functions of membranes 

 and cell walls see " General Discussion " [1937]. 



