18 Changes in Muscle during " Latent Stimulation" [May 1, 



in the same direction, and that at the cessation of the current the 

 meniscus does not return, or returns very slowly, describing on the 

 photographic plate a curve, of which the characters will be discussed 

 in a paper to be shortly submitted to the Society by Mr. Burch. It is 

 sufficient to say that the reason why the meniscus returns so slowly is 

 that the potential of the charge which it has received is proportional 

 to the displacement ; in the case of a current of very short duration it 

 is inconsiderable as compared with the difference of potential of the 

 terminals at the moment that the current is broken. 



When, instead of a single current in one direction (one two-hun- 

 dredth second), two currents of the same duration follow each other in 

 opposite direction, the record resembles in its essential characters that 

 of the excitatory electrical response in muscle. It is seen that the 

 mercurial column, which is displaced during the brief duration of the 

 first current, returns abruptly to the previous position during the 

 second. These phenomena I leave also to be discussed subsequently, 

 noting only that the difference of potential at the terminals of the 

 electrometer which is required to bring back the column to its original 

 position is the same as that by which it was displaced, and that such 

 an effect as has been described in muscle could not be produced by the 

 becoming negative of the middle of each muscular fibre, unless that 

 change were followed either by another in the opposite direction at 

 the seat of excitation, or by a similar change at the other electrode. 



Considering that the known velocity of propagation of the excita- 

 tory process in the muscle of the frog is about 3 meters, and that the 

 distance between the contacts is about 1*5 cm., we should expect that 

 if the two currents through the electrometer, the existence of which 

 the photographic record so distinctly indicates, were due to propaga- 

 tion, they should follow each other at an interval of one two-hun- 

 dredth of a second. The actual difference of time between the two 

 electrical effects lies fairly within this estimate. 



Postscript, April 28th. Since sending this communication, I have 

 become aware of a research published very recently by Professor 

 Bernstein (" Ueber den mit einer Muskelzuckung verbundenen Schall 

 und das Verhaltniss desselben zur negativen Schwankung." ' Unter- 

 such. aus dem Physiol. Institut der Universitat Halle,' 1890), which 

 relates closely to the subject of this paper. The facts observed, 

 though of a different order from those recorded above, afford a 

 remarkable confirmation of them. They are as follows : When a 

 muscle (gastrocnemius of a rabbit) is excited by a single induction 

 current applied to its nerves, its tendon and muscular surfaces 

 respectively being connected with a telephone, the electrical response 

 can be heard telephonically. This Bernstein calls the electrical thud 

 (electrischer Stoss). A thud of a similar character may be heard by 



