390 Royal Society :— 



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 glass plate in the manner above de- 

 scribed, that is, I press this strip of glass slightly on the middle of 

 the thigh on one side, and at the same time the extremities of the 

 two woollen cords come to rest on the cushions. The movements of 

 the needle are observed through a telescope (lunette). I have re- 

 peated this experiment thirty or forty times. Sometimes, and this 

 case is the most frequent, the first deviation produced by the muscle in 

 repose is directed in the same sense as that of the current of the 

 gastrocnemius ; sometimes the current is null, or almost null ; some- 

 times, and this case is the most rare, the deviation is in a contrary 

 direction, and this occurs most frequently in operating on the hinder 

 portion of the thigh. 



In all these experiments, the moment that the thigh begins to 

 contract, the needle moves in a constant direction ; the deviation 

 which intervenes is greater or less according to the force of the 

 contraction, and indicates constantly a descending discharge or 

 current of extremely short duration, which traverses the thigh in the 

 direction of the ramification of the nerves, and in a contrary direction 

 to the current of the gastrocnemius. 



"An Inquiry into the Muscular Movements resulting from the 

 action of a Galvanic Current upon Nerve." By Charles Bland Rad- 

 cliffe, M.D., F.R.C.P. 



In a lecture delivered about two years ago*, in which he treats 

 * Lectns sur la Physiologic ct Pathologic du systome ncrvcux. Tome 1. 

 LeconlO. Paris,. 1858. 



