THE PHYSIOLOGICAL EFFECTS OF IONS 453 



I undertook the determination of the physiological effects 

 of the ions of a series of electrolytes on frog's muscle. It 

 seemed essential to my mind, however, to choose such reac- 

 tions as are capable of exact quantitative determination. As 

 such reactions I chose first of all the amount of water ab- 

 sorbed by a muscle under the influence of certain electrolytes ; 

 for I had found that the gastrocnemius muscle of the frog, 

 which has, as is well known, usually about the osmotic pres- 

 sure of a 0.7 per cent. NaCl solution, increases considerably 

 in weight upon the addition of a trace of an acid or an alkali 

 to this sodium-chloride solution. This increase in weight is 

 chiefly due, no doubt, to the absorption of water. The second 

 reaction which I chose was the influence of the electrolyte 

 on the threshold of stimulation. As a source of stimulation 

 I used induction shocks, and as the measure of the threshold 

 of stimulation, the greatest distance at which the secondary 

 coil could be moved away from the primary and just appre- 

 ciable contractions still take place. I attach less value to the 

 latter method, because it seems to me that the irritability of 

 the individual muscle fibers does not vanish at the same 

 moment. When the electrodes are placed at one point, no 

 effect may be appreciable; when they are moved, however, 

 a slight twitching of individual fibers may yet be brought 

 about. This method can, therefore, not be considered as 

 accurate as the first method. 



II. EXPERIMENTS WITH ACIDS 



1. The normal solutions used in these experiments were 

 made with the greatest care by Dr. Bernhard, assistant in 

 the chemical laboratory. Solutions of the acids and alkalies 

 were made which were one-tenth normal with reference to 

 the H and OH contained in them. The HC1 solution, for 

 example, contained 1 gram -molecule (1 mol.) HC1 in 10 liters 

 of water; the H 2 SO 4 solution, only ^ mol. H 2 SO 4 in 10 



