310 Royal Society : — 



oif about the middle ; a knife being slipped behind the lumbar 

 plexus of nerves, the pelvic bones and contiguous soft parts are cut 

 away, so that the lumbar vertebrae remain connected with the lower 

 extremities merely by the nervous cords passing to each limb. Thus 

 prepared, the limbs are laid on a thin piece of board, so that the 

 vertebrae hang over its edge dangling by the undivided nerves. The 

 piece of board is placed floating on the surface of the w^ater in which 

 are the Actiniaj, and is slowly pushed over within reach of an active 

 one. Immediately that the Actinia seizes the morsel thus offered to 

 it, contractions are observed to commence in the thigh, extend to the 

 calf, and soon the toes are in movement. 



3rd. In order to set aside the supposition that these muscular con- 

 tractions might be the result of chemical or mechanical irritation 

 applied to the extremities of the nerves, it became necessary to devise 

 a modification of the foregoing experiments ; for although irritants, 

 such as turpentine, croton oil, ammonia, friction with a nettle leaf, 

 &c., were applied to the nerves without producing any effect like 

 that obtained from the Actiniae, it seemed still possible that the con- 

 tractions might be due to some other agent than electricity. 



The following experiment seems to remove all doubt. A piece of 

 copper wire, a few inches long, was coated with sealing-wax, except 

 about half an inch at each end ; the ends were rubbed clean with 

 sand-paper, one of them was thrust into the lower part of the spinal 

 canal of a frog prepared as in the last experiment, while the other, 

 which was to be offered to an Actinia, was passed into a portion of 

 the frog's intestine put on like a glove ; for the Actinia does not 

 seize vigorously metallic substances. The limbs of the frog with the 

 nerves and vertebrae attached, are laid on a piece of board, while the 

 copper wire, which is curved, arches over the edge of it ; so that the 

 end covered with frog's intestine can be readily brought within the 

 reach of the Actinia. Having waited for a few minutes until the 

 muscular contractions excited by thrusting the wire into the spinal 

 canal have ceased (and they are in general very transient), the board 

 is placed floating on the water, and the frog's intestine offered to an 

 Actinia; muscular contractions ensue, perhaps not so promptly, 

 certainly not so vigorously as in the former experiments, but never- 

 theless easily to be recognized and unmistakeable. They commence 

 in the thighs, and, as in the former case, extend to the calves, and 

 then the toes move actively. This last experiment has been modified 

 in a variety of ways, but the same result has been constantly obtained. 

 Perhaps the best modification of it is to use a piece of copper wire 

 having one end coiled so as to form a disk which is covered with 

 chamois-leather, while the other is sharp-pointed to enter the spinal 

 canal of the frog. The whole, except the surface of the disk, which 

 is to be given to the Actinia, and the point for the spinal canal, is 

 covered with sealing-wax, and the frog's limbs extended upon a thin 

 piece of board. With this arrangement precisely the same effects 

 were produced as already described. 



It is a remarkable fact, and deserves special notice, that in all 

 these experiments the muscular contractions, when once strongly 



