APPLICATIONS OF THE GRAPHIC METHOD. 183 
of the first has passed away, the result depending on the phase 
of the contraction, during which the stimulus acts on the mus- 
cle. Thus, if a second shock be applied during the latent pe- 
riod, no visible change in the nature of the muscle-curve can be 
seen; but if during one of the other phases of contraction, a re- 
sult like that figured below (Fig. 180) follows. If a series of 
such shocks be sent into the muscle before its contraction pe- 
riod is over, a succession of curves may be superposed on one 
PAPE Parra rps si eae restr ese e rst iL sire steers ee sap tir istieizis 
&. n m n m bl n 
Fic. 181.—Curve of imperfect tetanic contraction (Foster). Uppermost tracing indicates con- 
tractions of muscle ; intermediate, when the shocks were given ; lower, time-markings of 
intervals of one second. Curve to be read, like others, from left to right, and illustrates at 
the end a ‘* contraction remainder.” 
another, to the total height of which, however, there is a limit, 
no matter what the strength of the stimulus used. 
If the stimuli follow each other with a certain rapidity, such 
a tracing as that represented in Fig. 181 is obtained; and if the 
rapidity of the stimulation exceeds a certain rate, the result is 
that seen in Fig. 182. 
a 
Fia. 182.—Curve of complete tetanic contraction (Foster). 
It is possible to see in these tracings a genetic relation, the 
second figure being evidently derivable from the first, and the 
third from the second, by the fusion of all the curves into one 
straight line. 
If a muscle, isolated as we have described, be watched dur- 
ing the period that it is writing the second and the third 
