ELECTRICAL RELATIONS OF MUSCLE. 



819 



produced until more than 75 shocks are communicated in a second, whilst 

 the muscles of a tortoise are tetanized with only three shocks per second. 

 Ranvier 1 found considerable difference in the reaction of the white and red 

 muscles of rabbits to induce electricity. Thus the semitendiuosus (a red 

 muscle) excited for one-seventh of a second with a current that was inter- 



FIG. 295. 



rupted 357 times in a second, passed at once into a state of tetanus, and its 

 myographic tracing exhibited a continuous and uniform elevation. The 

 adductor longus on the other hand (a pale muscle), stimulated in the same 

 way, showed as many elevations and depressions as there were interruptions 

 of the current. 



668. The contractility of the muscles may be called into play either 

 directly by stimuli applied to the tissue itself, or indirectly by agents ex- 

 citing the motor nerves. The contraction which follows in the latter instance 

 is termed by Schiff neuro-muscular, and in the striated muscles is sudden, 



FlQ. 296. 



general, and energetic ; but when mechanical irritation is directly applied 

 to a muscle, the tissue itself responds to the stimulus, producing what Schiff 

 has termed idio-muscular' contraction. It may be observed in the manner 

 first described by Dr. Stokes 2 by percussing the pectoralis muscle of ema- 

 ciated patients, or by drawing the back of a knife across a muscle after all 

 signs of irritability on the application of stimuli to the motor nerve have 

 ceased ; it then presents itself as a swelling or intumescence a few lines 

 broad and high, but varying with the strength of the blow, lasting for four 



1 Brown-Sequard's Archives de Physiol., 1874, t. vi, p. 5. 



2 On Diseases of the Chest, p. 397.' 



