7 6 PHYSIOLOGICAL PHYSICS. [Chap. vn. 



the muscles, but a flag arrangement on each side of it. 

 The two muscles are thus clamped in the same forceps, 

 but are directed opposite ways, so that the tendo 

 Achilles of one is fixed to the thread passing over the 

 pulley of the signal at one side, and that of the other is 

 fixed to the pulley of the other side. The nerve from 

 each preparation is laid over the same platinum 

 electrodes. Wires from the secondary coil of an in- 

 ductorium are led to the middle cups of a commutator 

 without the cross. From one side of the commutator 

 wires proceed to the platinum electrodes ; from the 

 other side wires are carried directly to the muscles, one 

 wire being attached to the hook in the tendon of each 

 muscle. Thus, when the commutator is laid over to 

 the one side, the induction current is sent to the 

 nerves ; when it is reversed, the current passes straight 

 through both muscles. First, then, stimulate by the 

 nerves. It is found that only the muscle of the un- 

 poisoned frog contracts, then stimulate the muscles 

 directly and both contract. The muscle, therefore, whose 

 motor nerves have been destroyed is still capable of re- 

 sponding to a stimulus by contraction. Another way 

 of performing the experiment is to ligature the artery 

 of one limb of a frog, or simply tightly ligature one 

 limb at the upper part, and then inject the woorara 

 solution under the skin of the back. The ligatured 

 limb receives no poison. In about half-an-hour the 

 frog is paralysed with the exception of the ligatured 

 limb. Make two preparations with the two limbs, and 

 it is found, as before, that while both muscles respond 

 when directly stimulated, only one responds when the 

 stimulus is applied to the nerves. 



