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,’ 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 faeces 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 hyperesthesia 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 as my present experiments go, AICl,, and 
sodium-citrate solutions. The way of proceeding is as fol- 
lows: A number of solutions, say AICl,, are prepared, 
namely, 7%, 7%, %, ", and possibly % Then the weakest 
1CUSHNY AND WALLACE, American Journal of Physivlogy, Vol. I (1899). 
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