486 STUDIES IN GENERAL PHYSIOLOGY 



preparations. When a spark passes there is nothing to 

 keep the electricities in the muscle preparation apart, and a 

 current consequently passes longitudinally through the 

 nerves and causes the muscles to contract. 



6) The muscle preparations lie at a right angle to the path 

 of the spark, but in a position symmetrical with reference to 

 the spheres of the discharger (Fig. 140). The electricities 

 will now be distributed in the preparation in such a way 

 that during the passage of the spark a current must pass 



4- 



FIG. 141 



transversely through the nerve. Since the nerve cannot be 

 stimulated by a current passing transversely through it, the 

 effect is in this case minimal. 



c) The nerve-muscle preparations again lie parallel with 

 the spark discharge, but not in a position symmetrical with 

 reference to it, but toward one side of it (Fig. 139). The 

 electricities will now be so distributed that during the dis- 

 charge a current must pass transversely through the nerve. 

 We must therefore again expect a minimal effect, etc. 



The experiment with a mirror which I described in a 

 previous paper, and which at first seemed to contradict our 

 explanation, can also be explained in this way. The nerve- 

 muscle preparations, were placed at right angles with the 

 spark discharge, but not in a position symmetrical with the 

 discharger, but slightly to one side of it (Fig. 142). Under 

 such circumstances only a weak current passes longitudi- 

 nally through the nerves during the passage of the spark. 



