W. J. V. OSTERHOUT 7 



for various mixtures of NaCI and CaCl2 were ascertained; these are 

 given in Table I.'^ 



There are two points of principal importance in the consideration 

 of these constants: (1) It was shown in a former paper '^ (which 

 dealt with net resistance only) that the value of /v 4 ~ Km increases 

 regularly as the per cent of CaCl-i in the surface of the cell increases. 

 That this is also true in the case of protoplasmic resistance is evident 

 from Fig. 2. (2) It was also pointed out that as the per cent of 

 CaCl2 in the solution decreases from 62 to 1.41 per cent the value of 

 Km first decreases (reaching a minimum at 4.76 per cent) and then 

 increases. It was found that the amount of decrease corresponds to 



.02 



X = Increase in Ka+Km 



.01- 



12.50 20 33.33 63.73 84.34 94.22 100 



Ca CI 2 in sur|ace 



Fig. 2. Ordinates represent the increase in value of Ka -^Km and of Kap -^Kmp 

 In each case the value given represents the increase over the corresponding value 

 in the solution containing 1.41 per cent CaCU (the corresponding per cent in the 

 surface being 12.5). Abscissae represent per cent of CaCU in the surface. In 

 order to facilitate comparison the values of Kap -^Kmp have been divided by 1.685. 



^^ These are approximate values, obtained graphically. The constants of the 

 curves of protoplasmic resistance are designated as Kap (corresponding to Ka) 

 and Kmp (corresponding to Km)- The curves of protoplasmic resistance may 

 show less inhibition at the start than those of net resistance. 



^^Osterhout, W.J. V., J. Gen. Physiol., 1920-21, iii, 415. 



