ELECTRICAL CHANGES IN MUSCLE 259 



for a time in water, it passes into a condition known as ' water rigor,' 

 in which it is incapable of contracting, although capable of trans- 

 mitting an excitation from one end of the muscle to the other. 



The connection of a diphasic current of action with an excited 

 condition of the tissues passing as a wave from one end to the other 

 is shown still more clearly on a slowly contracting tissue, such as 

 the ventricle of the frog or tortoise. Fig. 88 A is a photographic record 

 of the variation obtained from the tortoise ventricle, which is led 



A 



B 



FIG. 88. Electrometer records of the electrical variations in a tortoise 

 ventricle, excited to beat rhythmically by single shocks. A. Ventricle 

 uninjured. B. One leading off spot injured. (B. SANDERSON.) 



off to a capillary electrometer, one (acid) terminal being connected 

 with the base of the ventricle, the other (mercury) with the apex. 

 Each part of the ventricle remains contracted for a period of 1J to 

 2 seconds, and then the contraction passes off, first at the base and 

 later at the apex. The electrical events are an exact replica of the 

 mechanical. Directly after the stimulus has been applied, the base 

 becomes negative and the column of mercury moves up. A moment 

 later the excitatory condition extends to the apex, There is thus a 

 sudden equalisation of potential between the two terminals, and 

 the mercury comes back quickly to the base line, Here it stays for 



