760 STUDIES IN GENERAL PHYSIOLOGY 



the one which, I believe, was first suggested by Schmiede- 

 berg, namely, that these salts prevent the absorption of 

 liquids from the intestine, and that this retention of liquids 

 causes the cathartic effect. I will not deny the effect of these 

 salts upon the phenomena of absorption of water from the 

 intestine, 1 but it is obvious from our experiments that the 

 same salts must increase the irritability of the nerves and 

 muscles of the intestine, and that this must facilitate the 

 production of peristatic motions, possibly through the mechan- 

 ical or contact-stimuli of the fseces upon the nerve-endings 

 or the muscular wall of the intestine. 



2. These experiments suggested the idea whether or not 

 electrolytes are capable of producing also a hypersensitive- 

 ness of the skin and conditions that may be comparable to 

 the conditions of hypersesthesia or hyperalgesia. It is well 

 known that when we suspend a pithed frog vertically so that 

 its legs hang down, the latter will be lifted at once when 

 they are dipped into an acid or alkali of a certain concentra- 

 tion, while no such reaction occurs when they are dipped 

 into water. The reaction of the animal to acid may be so 

 violent as to suggest to a layman the idea that it is suffering 

 intense pain. I wondered whether by an alteration of the 

 nature and proportion of ions in the skin the sensitiveness 

 could be increased or varied in such a way as to make the 

 skin as sensitive to the contact with pure water as it natur- 

 ally is to strong acid. The experiments resulted in my find- 

 ing certain solutions of electrolytes which did not seem to 

 affect the animal directly, but yet made it extremely sensi- 

 tive toward contact with water. The best solutions for this 

 purpose are, as far a my present experiments go, A1C1 3 , and 

 sodium-citrate solutions. The way of proceeding is as fol- 

 lows: A number of solutions, say A1C1 3 , are prepared, 

 namely, f|, "^ , , and possibly f. Then the weakest 



1 CUSHNY AND WALLACE, American Journal of Physiology, Vol. I 



