FLEISCHL'S RHEONOM. 155 



electrodes are attached. See that the battery and induction 

 machine are perfectly insulated by supporting them on 

 blocks of paraffin. 



(b.) Prepare a nerve-muscle preparation, and arrange it in 

 the muscle-chamber in the usual way, laying the nerve over 

 the electrodes. One ol the electrodes will therefore be con- 

 nected with the secondary circuit. 



(c.) Make and break the primary circuit, there is no con- 

 traction. 



(d.) Destroy the insulation of the preparation by touching 

 the muscle, or what does better, allow the brass support of 

 the muscle to touch a piece of moist blotting-paper on the 

 inner surface of the glass shade of the chamber. Every 

 time the brass-binding of the shade is touched, or the brass 

 support itself, the muscle contracts. Touch the secondary 

 coil and contraction results. 



LESSON XXIX. 



RHEONOM TELEPHONE EXPERIMENT- 

 DIRECT AND INDIRECT STIMULATION 

 OF MUSCLE RUPTURING STRAIN 

 OF TENDON MUSCLE SOUND 

 DYNAMOMETERS. 



1. Fleischl's Rheonom. This instrument (Fig. 57) is very use- 

 ful for showing du Bois-Reymond's law, that it is variations in 

 the density of a galvanic current which 

 excite a motor nerve. It consists of a 

 square ebonite base, with a grooved circular 

 channel in it, and two binding screws, 

 with zinc attached, and bent over so as to 

 dip into the groove, which is filled with a 

 saturated solution of zinc sulphate. A 

 vertical arm, with binding screws attached 

 to two bent strips of zinc, moves on a 

 vertical support. Fig> 5 7 ._ F iei sc hl's 



Rheonom. 



