586 



PHYSIOLOGY. 



Fig. 221. Schema of Experiment to Measure the Rapidity of the 

 Muscle Current by the Aid of the Differential Rheotome of Bernstein. 

 (LAHOUSSE.) 



M, Muscle prepared in such a manner that by one extremity the muscle 

 current goes to the galvanometer, and to the other extremity electrodes are 

 applied which carry to the muscle an induction current. O, Galvanometer. 



The rheotome of Bernstein (A) consists essentially of a disc (B), which is 

 set in uniform and rapid motion by the rotation apparatus of Helmholtz (H). 

 At each revolution the needle C, striking the wire C', closes and opens rapidly 

 the primary current of the induction apparatus in such a manner as to excite 

 the muscle by a single induction current. On the opposite side of the disc lie 

 two needles (D, D) which, dipping in the two cups of mercury (D f , D'), close 

 for a very short time the circuit of the muscle current. If the rapidity of 

 rotation of the disc is known and the interval which elapses between the time 

 of excitation of the muscle, that is, the time when the needle (C) strikes against 

 the wire (C'), and the beginning of the closing of the muscle current, that is, the 

 time when the two needles (D, D) commence to dip into the mercury cups 

 (D f , D'), then the rapidity of the propagation of the negative wave or variation 

 is easily calculated. 



