346 



As to Dr. Radcliffe's first remark, I shall only observe that in 

 the principal experiment the needle does not merely move slowly 

 towards zero during contraction, but is seen, during the first con- 

 tractions, especially when the frog operated on is vivacious, to move 

 rapidly down to zero, to oscillate, to pass to the opposite side, and 

 sometimes even to remain fixed, while thus deviated, for a very short 

 interval of time. This result, which is easily obtained and can be 

 verified without difficulty, is the same, whether the electrodes are 

 of platinum, like those employed by M. du Bois-Reymond, or of 

 zinc. 



It is easy to understand that, in order to succeed in these experi- 

 ments, it is desirable that the needle should be as little deviated as 

 possible before the contractions : this object is best ensured in the 

 following way : I prepare the frog by reducing it to two thighs, 

 leaving a single lumbar nerve in order to obtain contractions in one 

 of the thighs. Instead of saturated solution of sulphate of zinc, I 

 employed a weak solution of this salt, in order to avoid any alteration 

 of the surface of the muscles ; and finally, in order to maintain exactly 

 the same points of contact between the two electrodes and the two 

 near points of the middle portion of the thigh, I employ two fine 

 woollen cords or two thin strips of card-board fixed with sealing-wax 

 on a plate of glass and soaked in the same solution. The experi- 

 ment is made by applying the glass plate with a certain pressure 

 on the thigh, so that the two cords on one side touch the thigh, and 

 on the other are placed in contact with the cushions of flannel or 

 card-board which are immersed together with the electrodes, accord- 

 ing to the method followed by M. du Bois-Reymond. 



I think it useful to describe in a few words a little apparatus 

 which affords a good deal of facility for making these experiments. 

 It consists in a small square block of wood, with a cavity deep 

 enough to receive the electrodes and the cushions. It is hardly 

 necessary to say that this cavity is coated with a varnish of sealing- 

 wax and divided in the middle by a glass plate. Another cavity in 

 the same block serves as a recipient for the two thighs ; the sciatic 

 nerve extends beyond the block, and rests on two platinum wires 

 which communicate with the pile or with the electro-magnetic ma- 

 chine. The communication between the thigh and the electrodes is 

 established by means of the glas^ plate in the manner above de- 



