FROM THE SMALL INTESTINE 627 



is true of similar solutions of electrolytes, no matter what 

 property a more dilute solution has. The way in which these 

 hypertonic solutions cause stimulation is uncertain, but it seems 

 likely that they act largely by the extraction of water setting 

 up a definite change in the colloids of the cell. 



When we turn to solutions of electrolytes containing ions, 

 we see that they might act on living cells, apart from osmotic 

 pressure, in two ways either chemically or electrically. The 

 subject is still highly theoretical, and nothing more than a very 

 brief outline can be attempted. The subject has been investi- 

 gated by Hardy, Loeb, and many other observers, and recently 

 by Mathews, Garrey, and Benedict for nerve, skeletal muscle, and 

 cardiac muscle respectively ; and in their papers the necessary 

 references to previous workers can be found. Electrolytes, like 

 non-electrolytes, can stimulate nerve by an osmotic abstraction 

 of water. Mathews found that nearly all electrolytes in solutions 

 having an osmotic pressure of about 14 atmospheres will 

 produce stimulation. But electrolytes, unlike non-conductors, 

 may also produce stimulation as isotonic solutions, therefore it 

 is clear that they have some further power of stimulation, which 

 might be either chemical or electrical ; and we have to discuss 

 which it is. Now, since nearly all sodium salts stimulate nerve 

 the chemical composition of the anions in this instance must 

 be unimportant ; and the stimulating power of these salts might 

 be looked upon as a peculiarity of the cation Na. But we find 

 that many salts of ammonium, potassium, barium, lithium, and 

 rubidium share their power with sodium salts : and we are 

 obliged to conclude that this power does not appear to be a 

 peculiarity of the chemical composition of the cation any more 

 than of the anion. Solutions of KOH or NaCl produce the same 

 stimulatory effect on nerve, and yet the only thing they have 

 in common is nothing chemical, but the point that both are 

 electrolytes. Both solutions contain positive and negative 

 particles, and since the chemical composition of these ions appears 

 to be a matter of indifference, we can conclude only that their 

 properties depend upon their electrical condition ; in other words, 

 we come to the conclusion that chemical stimulation is essentially 

 electrical stimulation. Now, if this is so, we should expect that 

 the anion of NaCl would be the stimulating agent ; for, having 

 a negative charge it would correspond to the cathode or negative 



