520 STUDIES IN GENERAL PHYSIOLOGY 



The contractions of a heart preparation fed by an alkaline salt 

 solution are much more regular and even than the contractions of 

 a sartorius preparation; it is to be particularly emphasized that in 

 the first case all the muscle fibers contract evenly and simultane- 

 ously, while, as has been pointed out above, in a sartorius immersed 

 in a salt solution it is the rule that the primitive fibers never con- 

 tract simultaneously and equally strongly; much oftener the con- 

 tractions observed are local, and the rhythm of the various local 

 contractions may vary most decidedly. 1 



This difference between the periodic contractions of the 

 muscle and those of the heart holds also in the experiments 

 which I give below. I do not believe, however, that we can 

 conclude from these differences that there are differences in 

 the manner in which the rhythmical activities in the two 

 cases originate. We cannot, for example, conclude from this 

 that the difference is determined through the influence of 

 the ganglion cells in the heart. I believe that we deal, 

 partly at least, with a difference in conductivity. In the heart 

 muscle the stimulus can pass from element to element. If, 

 therefore, only one element is stimulated and caused to con- 

 tract, the whole heart must become active. In skeletal 

 muscle the sarcolemma prevents such a passage of the stimulus 

 from element to element, and we obtain in consequence irregu- 

 lar isolated contractions of the individual fibers. The case is 

 similar to that observed in Medusae, in which we find a syn- 

 chronous activity of all the elements when the continuity of 

 the elements is complete, and a loss in synchrony when the 

 conductivity between the elements is diminished. 2 



3. We will now return to our main problem, and endeavor 

 to answer the question whether only certain ions are able to 

 bring about rhythmical contractions in muscle. 



I tested first of all Biedermann's assertion that these 



1 BlEDEKMANN, IOC. tit. 



2 Engelmann and Romanes have pointed out this fact. A discussion of this sub- 

 ject is found in my Comparative Physiology of the Brain (New York: Putnam's 

 Sons, 1900). 



