116 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



rate of stimulation required for the production of this condition depends 

 largely upon the character of the muscle, and its condition at the time. In 

 the experiment recorded in Figure 47 the development of the condition of con- 



FIG. 47. Effect of frequent excitations to gradually produce tetanus. Experiment on a gastrocnemius 

 muscle of a frog, similar to the last. The weight was only 10 grams. The rate of excitation was 100 per 

 minute. This muscle had been worked a short time before this series of contractions was taken, and, as 

 a result, the introductory and staircase contractions were absent and contracture began much sooner 

 than in the experiment recorded in Figure 45. The record in section 6 is a continuation of that in 

 section a. 



tracture was more marked than in the above experiment, and the resulting con- 

 dition of continued contraction caused first incomplete and finally complete 

 tetanus. 



Although frequent excitations appear to be essential to the development of 

 contracture, it is doubtful whether it is to be considered a fatigue effect, since 



FIG. 48. Development and fatigue of contracture. Experiment on a gastrocnemius muscle of a frog. 

 The weight was 10 grams. As in the preceding experiments strong maximal breaking induction shocks 

 were used to excite. The rate of excitation was 5 per second. The record appears as a silhouette for the 

 reason that the drum was moving very slowly. 



the contracted state which it produces may be increasing at the time that fatigue 

 is lessening the height of the ordinary contraction movements, and since the 



