NEW CONCEPTIONS IN SCIENCE 



ago from some brilliant experiments of Professor 

 Albert P. Mathews, of the University of Chicago, 

 which I have already recounted. It will be re- 

 membered that Professor Loeb and others had 

 shown that in certain salt solutions an excised 

 heart could be kept beating for hours ; further, that 

 a piece of ordinary muscle frog's muscle, for ex- 

 ample dipped in these same solutions would beat 

 rhythmically, like a heart. All of these curious 

 manifestations could be varied, the rhythmical 

 play hastened, retarded, or stopped, simply by 

 changing the quantity of salts in the solution or by 

 adding different salts. A pinch of one salt, like a 

 potassium salt, would hinder the effect of another, 

 such as ordinary table-salt (sodium chloride). 



Professor Mathews took a step further. Instead 

 of cutting away the nerves from the muscles, he 

 left them joined at one end, merely separating the 

 nerve enough to let it hang in a cup of salt solution 

 while the frog's legs were suspended on a frame. 

 The rhythmical beat began in a short time, just as 

 if the muscles themselves were in the salt -bath. 

 Plainly the nerve carried the stimulus, and, so far 

 as any mortal could see, that stimulus was the same 

 as that which makes a live frog's muscles contract 

 when it jumps. Whence came this stimulus? 



The only solutions which give this effect are 

 those which generate an electrical current. A suc- 



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