554 PHYSIOLOGY. 



relax; thus, the second contraction encroaches upon the first, the 

 third upon the second, etc. From the rapid succession of the stimuli, 

 the muscle remains in a condition of continued vibratory contraction. 

 That is, in a state of tetanus. 



Complete Tetanus. If the excitation rhythm be more frequent, 

 say, fifty of them per second, there will no longer be any trace 

 of the primitive shocks. The ascent of the muscle-curve will be 



Fig. 200. 1. Imperfect Tetanus, 15 Contractions per second. 

 2. Perfect Tetanus. (LAULANifi.) 



abrupt and decided; the contraction due to the first shock will not 

 be followed by any relaxation. There will be no oscillation recorded 

 upon the myogram. The upper straight line due to the complete 

 contraction of the muscle is called the plateau. When the muscle 

 is in this condition the tetanus is said to be perfect or complete. 



The tetanus is spoken of as incomplete when there are still relax- 

 ations and vibrations which indicate the incomplete mingling of the 

 shocks. 



The number of stimuli that are required to produce tetanus may 

 be very variable. Fifteen to twenty stimuli per second suffice to 

 throw a frog's muscle into tetanus. 





