240 M. L. BASKERVILL. 



There has been little work reported on the effect of NaCl 

 and CaCls on cell permeability to non-electrolytes. The number 

 of papers relating to the effect of these salts on permeability to 

 other electrolytes, or concerned with their effects in general on 

 cell permeability, have been so many that only a few typical ones 

 to illustrate the different kinds of studies may be mentioned here. 

 Osterhout (i) showed that there is a difference of conductivity 

 with different proportions of NaCl and CaClo in the case of 

 various plants, and he proved that this also holds true for frog 

 skin (2). However, in a more recent paper (3) he has expressed 

 the view that an increase of conductivity does not necessarily 

 indicate a greater permeability to ions in the absence of electric 

 currents. Harvey (4) noted that NaOH enters Spirogyra cells more 

 easily from a NaCl solution than from a mixture of NaCl and 

 CaClo. R. Hamburger (5) found that artificial edema may be 

 produced by solutions lacking calcium. In 1909 R. S. Lillie (6) 

 reported that pure isotonic solutions of sodium salts increase the 

 permeability of the pigment-containing body cells of Arenicola 

 larvae, while this effect is prevented by addition of CaCl 2 . Many 

 other papers by the same author refer to similar effects of these 

 salts in relation to permeability. In a paper dealing with 

 artificial parthenogenesis, Lillie and Baskervill (7) assumed that 

 the greater effect of NaCl as compared with mixtures of NaCl 

 and CaCU in causing development is due to the increase of 

 permeability in the former case. Since it has been so often 

 assumed that NaCl will increase the permeability of tissues 

 for all substances and that certain proportions of CaCl 2 will 

 decrease permeability, it seemed desirable to ascertain how 

 much the salts in question might influence the permeability of 

 frog skin for a non-electrolyte, urea. 



The skin used was obtained either from the bull frog, Rana 

 catesbiana, or from Rana virescens, and was removed with as 

 little injury as possible. Usually it was tied over the end of a 

 glass tube 16 mm. in diameter. In a few experiments the skin 

 from a whole leg tied at the distal end to form a sac was used. 

 Measured amounts of the salt solutions under investigation were 

 put into the tube or sac. The skin was then immersed in a 

 bottle containing 50 to 100 cc. of urea solution, an amount 



