APPENDIX I. 125 



cylinder to the time spent by the wave of contrac- 

 tion in travelling from the first to the second 

 crutch. The velocity of the contraction thus ob- 

 tained, falls as much short of that anticipated by 

 theory, as did that of the nervous agent ; being, in 

 fact, even in muscles fresh from the body of the 

 frog, only about one yard in one second.* 



Time required for Reflex Action in the Spinal 

 Cord. The conduction of sensation in the spinal 

 cord, according to Dr. Schelske's above-mentioned 

 experiments, takes place at nearly, perhaps quite, 

 the same rate as in the nerves ; but a great delay is 

 occasioned by the so-called reflex action, when the 

 sensation, impinging upon the spinal cord, starts an 

 involuntary motion by the intervention of the 

 ganglionic cells. By experiments performed on 

 frogs poisoned with strychnia, Professor Helmholtz 

 has found that the reflex contraction happens from 

 -j^ to T T o- of a second later than the contraction 

 directly produced by the same induced current ; 

 from which observation it may be concluded, that 

 the reflex action in the spinal cord takes more than 

 twelve times the time required for the transmission 

 of the stimulation through the sensory and the 

 motor nerves. | This is doubly interesting, because 

 it was chiefly by the impossibility of catching with 



* Dr. Ch. Aeby, Untersuchungen uber die Fortpflanz- 

 ungsgeschwindigkeit der Eeizung in der quergestreiften Muslcel- 

 faser. Braunschweig, 1862. 



t Monatsberichte der Berliner Akademie der Wissens- 

 chaften, 1854. S. 332. 



