410 ELECTRO-PHYSIOLOGY CHAP. 



per second through the margin of the stroboscope, it follows that 

 the interrupting springs differ by two beats. Martins tested the 

 physiological applicability of the method (I.e. 592) by leading off 

 from longitudinal and transverse section of the frog's gastroc- 

 nemius to the capillary electrometer by unpolarisable electrodes, 

 the current of rest being compensated. On exciting the sciatic 

 by 18 break induction shocks per sec. the meniscus exhibited 

 regular and visible oscillations ; the stroboscope was then intro- 

 duced into the primary circuit of the induction apparatus, so that 

 the flag vibrated synchronously with the number of stimuli, 

 when the oscillations of the meniscus were extinguished thus 

 proving that a negative variation corresponds with each impact of 

 stimulation in the muscle, an oscillation of the capillary meniscus 

 with each negative variation. The same effect is produced with 

 a stimulation frequency of 30 per sec. Unfortunately, we have 

 thus far no systematic analysis of strychnin tetanus, spasm in 

 electrical excitation of the spinal cord, or the voluntary and 

 reflex movements of the frog, by this method. Loven's analysis 

 (43) of voluntary muscular contraction in the frog and crab with 

 the capillary electrometer yielded interesting results, and has 

 recently been confirmed by v. Kries. 



Loven convinced himself that the persistent voluntary con- 

 traction of the crab's muscles, as well as strychnia spasms in this 

 animal and the frog, are accompanied by definite and fairly 

 regular variations of current. The frequency of these was 

 astonishingly low (about 8 per sec.) That such infrequent 

 twitches should fuse into a persistent contraction is the more 

 remarkable, since we know that 20 or more excitations per 

 sec. are required to produce complete tetanus on the frog with 

 electrical excitation, and according to v. Limbeck's observations 

 34 stimuli sent into the spinal cord can be transmitted to the 

 muscle. Loven finds himself reduced to the hypothesis that 

 single voluntary twitches travel more slowly than those provoked 

 by electrical excitation. These results tally with those of Del- 

 saux (44) (Fig. 136, a and &), who only observed five oscillations 

 per sec. with the frog's gastrocnemius in strychnia tetanus, on 

 the capillary electrometer. The simultaneous record of change 

 of form and electrical variation in muscle showed complete co- 

 incidence. 



Since the telephone, like the capillary electrometer, is ex- 



