STIMULATION' OF MUSCLE AND NERVE 101 



when the intensity is rapidly altered by making 

 or breaking the circuit. These experiments, 

 however, were made on the rapidly reacting 

 skeletal muscle of the frog. The law does not 

 hold good for sluggish contractile tissue. In- 

 deed it can be disproved even for highly striated 

 muscle by a very careful examination of the 

 manner in which excitation takes place. Pfluger 

 discovered that when the galvanic current is 

 made, excitation takes place only at the pointa 

 through which the current leaves the muscle or 

 nerve (cathodal stimulation), and that when the 

 current is broken, excitation takes place only 

 where the current enters the irritable tissue. 

 This "polar excitation" we must now consider. 

 We shall find, among many other facts, the 

 refutation of the idea that stimulation does not 

 occur throughout the passage of the current. 



POLAR STIMULATION OF MUSCLE . 



1. Slit the curarized sartorius muscle trouser- 

 like from the lower end. Lay each end on a 

 boot electrode. Make and break the current. 



On making the current the cathodal side will 

 contract; on breaking, the anodal side. 



2. Lay the muscle on ice covered with a small 

 piece of paraffin paper, to shield the muscle from 



