GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 115 



tween the succeeding stimuli, for contraction, will be excited before relaxation 

 is complete. As is shown in the record of the experiment reproduced in Figure 

 46, there will come a time in the work when the base-line connecting the lower 

 extremities of the succeeding myograms will be seen to rise in the form of a 

 curve, the change being at first gradual, then more and more rapid, and then 

 again gradual (see 6, Fig. 46). The effect of the change in the power to relax 

 is to make it appear as if the muscle were the seat of two contraction processes, 

 the one acting continuously, the other intermittently in response to the suc- 

 cessive excitations. Such a condition as that exhibited in section c, Figure 46, 

 is spoken of as an incomplete tetanus, complete tetanus being a condition of 

 continuous contraction caused by rhythmical excitations, in which none of the 

 separate contraction movements are visible. In complete tetanus the muscle 

 writes an unbroken curve. 



FIG. 46. Effect of frequent stimuli to gradually produce incomplete tetanus. Series of isotonic con- 

 tractions of a gastrocnemius muscle of a frog, excited once every two seconds by strong breaking induc- 

 tion shocks. Only a part of the record is shown, 70 contractions have been omitted between the end of the 

 section marked a and the beginning of section b, and 200 contractions between the end of section b and the 

 beginning of c. The increase in the extent of the relaxations seen at. the close of the record was due 

 to the slowing of the rate of excitations at that time. 



The slowing of the relaxation of the muscle and consequent state of con- 

 tinued shortening which is to be seen in the latter part of the above experiment 

 is termed " contracture." The amount of contractnre increases, within limits, 

 with the increase in the strength and rate of excitation. The intensity and 



