ELEMENTARY EXPERIMENTAL PHYSIOLOGY 33 



Cold tap-water saline solution, which has been cooled by ice to nearly 

 O c C., is slowly poured upon the muscle ; the temperature of the 

 solution is noted, the muscle is stimulated, its contraction recorded and 

 the point along the tracing at which the stimulus was sent into the muscle 

 is marked. Swing the writing point off the drum, but do not move 

 the base of the stand carrying the myograph. Take a series of super- 

 imposed curves at temperatures of about 3, 13, 23, and 33 C. (Fig. 

 38). Sufficient time must be given and fluid used to allow the bulk of 

 the thick gastrocnemius to attain approximately the temperature of the 

 saline solution. In order to get exact results, it would be necessary to 



FIG. 38. The effect of temperature upon the contraction of the gastrocnemius 

 muscle. The time is marked in TJJ^ second. The tracing should bi read from right 

 to left. Figures on curve are the temperatures of the salt solution. (Pembrey and 

 Phillips.) 



suspend the muscle in the solution at a given temperature until its 

 substance had attained that temperature. 



It will be seen that cold lengthens the whole curve, especially the 

 latent period and the phase of active contraction; the period of 

 relaxation is relatively less affected, but a tendency to incomplete 

 relaxation is often seen. 1 As the muscle is warmed, the liberation of 

 energy becomes more and more rapid, consequently the time occupied 

 by the whole twitch decreases progressively, and especially the latent 

 period and period of shortening; the passive stage of relaxation is 



1 Cooled excised muscles, even when weighted, are liable to show a ' contrac- 

 tion-remainder,' or incomplete return to their former length after contraction. 

 It is also seen after strong direct stimulation, in poisoning with veratrine, and as 

 fatigue or death come on. 



C 



