ELECTROLYTES IN LIVING MATTER 83 



generally correct. In solutions of dextrose, cane sugar, milk sugar, 

 and glycerine, no twitchings of the common muscles occurred, no 

 matter how concentrated the solution. In solutions of urea the same 

 was true, in general, but occasionally transitory contractions were 

 observed. In alcohol I also observed occasionally a slight twitching, 

 but it is possible that in these latter cases the twitchings were caused 

 by an indirect effect of urea and alcohol upon reactions or changes 

 inside the muscle fibers. On the whole, I am under the impression 

 that the muscle cannot be, or only exceptionally, and to a slight extent, 

 caused to contract by solutions of nonconductors. I found that the 

 same is true for the rhythmical contractions of the center of the jelly- 

 fish (Gonionemus). Dr. Lingle tried the same experiments on the 

 strips from the ventricle of the tortoise, with the same result. In pure 

 solutions of dextrose, cane sugar, and glycerine, no beats originated, 

 even if the strip remained in these solutions for a day; but when the 

 ventricle was afterward put into a pure NaCl solution the contrac- 

 tions began, showing that these solutions had only prevented the 

 contractions without permanently injuring the heart. Lingle also de- 

 termined what the minimum concentration of NaCl was that was able 



n 



to start heartbeats. He found that in a mixture of 98 c.c. - cane sugar 



4 



^7 W ^7 



+ 2 c.c. :- NaCl, or 96 c.c. - cane sugar + 4 c.c. NaCl, no beats 



8 W 4 n 



started; while with 90 c.c. -- cane sugar + 10 c.c. - NaCl beats could 



be produced. 



All these experiments seemed to support or, at least, not to contra- 

 dict the idea set forth in my first paper on this subject, that the rhythmical 

 contractions depend upon the exchange of Na (or K) and Ca (or Mg) in 

 certain compounds, possibly proteids or soaps, in the muscle. Such an 

 exchange might alter the physical properties, e.g. the surface tension, 

 or viscosity, etc., of the substance; and a sudden change in one of the 

 properties might result in a change of form such as underlies contrac- 

 tion. I figured to myself that the change starting rhythmical contrac- 

 tions was a sudden change in surface tension, e.g. a phenomenon of 

 spreading, and gave expression to this possibility in my book on Brain 

 Physiology. A series of new observations confirms me in the idea 

 that we are dealing here with phenomena which must occur at the 

 surface of the elements. 



In 1901 I described a form of irritability in the muscle which, to my 

 knowledge, had never been noticed before, and which is produced by 

 such salts as precipitate Ca or diminish the concentration of free Ca-ions, 

 such as citrates, oxalates, fluorides, carbonates, phosphates, etc., and 



