March 21, 1913] 



SCIENCE 



429 



weight of dissolved substances would be 

 warranted. 



The following gives the results of the 

 change in the volume of red blood cor- 

 puscles in isosmotic concentrations of 

 KNO, and NaCl. 



The agreement is best for .17 KNO3 which 

 was equi-molecular with the blood used in 

 this case. 



But even for concentrations differing 

 from the molecular concentration of the 

 blood the agreement is still surprisingly 

 satisfactory, considering the fact that solu- 

 tions which differ widely in their concen- 

 tration from that of the blood corpuscles 

 are liable to modify the permeability of 

 the cells, as we shall see later; and that 

 this injurious effect is influenced strongly 

 by the chemical nature of the substance. 



We may, therefore, state that equi-molee- 

 ular solutions of salts cause practically the 

 same change in the volume of red blood 

 corpuscles. 



The experiments on red blood corpuscles 

 have the disadvantage that we can not well 

 discriminate between the living and dead 

 cell. In this respect the experiments on 

 muscle are much more satisfactory. It had 

 been known through the experiments of 

 Nasse that in an m/8 solution of NaCl (and 

 other salts of Na) the frog's muscle keeps 



its weight. The writer showed sixteen 

 years ago that (wi'thin certain limits of 

 time) the same is true for solutions of 

 LiCl, KCl, MgCl^, CaCL, SrCU and BaCl^ 

 equi-molecular with an m/8 NaCl solution, 

 while in solutions of lower concentration 

 the muscle absorbs, in solutions of higher 

 concentration it loses water. He con- 

 cluded from this that the absorption of 

 water by the muscle is determined by van't 

 Hoff's law.* The number of molecules in 

 solution, and not their chemical character, 

 determines the exchange of water between 

 muscle and surrounding solution. 



I was interested to find out with what 

 degree of accuracy Avogadro's law deter- 

 mines the exchange of water in the muscle. 

 For this purpose a series of experiments 

 were made with NaCl and various sugars 

 in concentrations slightly below or above 

 the point of isotony. 



CHANGE IN WEIGHT OP A FROG'S MUSCLE WITHIN 



ONE HOUR IN PER CENT. OP ITS ORIGINAL 



WEIGHT IN 



.1 .125 .150 .175in NaCl 



+ 3.9% 0% —1.9% —1.9% 



In a .Im solution of NaCl the muscle takes 

 up water, in a .125m solution it keeps its 

 weight, in a .15 solution it loses water. 

 That the loss in a .175m solution was in this 

 case not greater than in a .15 solution was 

 accidental and probably due to the fact 

 that different muscles vary somewhat in 

 their osmotic pressure, owing to their pre- 

 vious history — e. g., whether they had been 

 more or less active. The influence of these 

 inequalities can be eliminated by making 

 a large number of experiments. 



But, although the muscle is not quite as 

 accurate an osmometer as the red blood 

 corpuscles, the fact that its exchange of 

 water is determined primarily by Avo- 



*Loeb, Pfluger's Archiv, Vol. 69, pp. 14-20, 

 1897. 



