380 INNERVATION. [CHAP. XI. 



extent of 5, 10, or 15 or more. The deviation could be increased by making 

 a chain of frogs' legs prepared in the same way. The legs were placed on an 

 insulating plane, so that the nerves of one touched the feet of the next, and so 

 on. It is necessary that the extremities of this pile should be plunged into 

 capsules filled with water. Or a pile may be made with a series of capsules 

 containing water connected together by frogs' legs ; the nerves being placed 

 in one, and the feet in the next. With such piles a deviation of the needle to 

 the extent of 60 may be obtained ; or to a much greater extent, if, instead of 

 distilled water, a weak solution of salt be employed to fill the capsules ; or still 

 more, if the fluid of the capsules be slightly acid. 



In all these experiments the direction of the electric current was found to 

 be constant, from the feet to the head. At the same time that the needle was 

 made to deviate, the frogs' legs, whatever be the number constituting the pile 

 are thrown into contraction. It is not necessary for the production of the phe- 

 nomena that the several legs should touch one another ; it will suffice if they 

 be connected by a conducting material, such as a skein of cotton moistened, 

 wire, wet paper, or even water. 



Nobili found that these signs of an electric current continued for many 

 hours after the preparation of the animal. He distinguished the current by 

 the title of le courant de la grenouille, ou courant propre ; and he attributed it 

 to a thermo-electric current caused by the unequal cooling of the nerve and 

 muscle produced by evaporation. 



It is evident, that the experiment of Nobili is essentially the same as the 

 original one of Galvani. In the latter, the electric current was brought to 

 act upon the nerves of the limb ; in the former, upon the galvanometer. 



The galvanoscopic frog maybe used as a test of the electric current when No- 

 bili's arrangement is preserved. If the extremes of the pile be connected by the 

 nerve of the galvanoscopic limb, the instant the circuit is completed, its muscles 

 will contract; and, as in other experiments with the galvanoscopic frog, we 

 may determine the direction of the current when the frog becomes a little 

 weakened. 



Matteucci gives the name " contraction propre" to the contraction of the 

 muscles which takes place in the frogs' legs, whether used singly or as a pile, 

 at the same time that the deviation of the needle occurs. In order to obtain 

 this phenomenon, the lumbar nerves must not be plunged completely in the 

 water ; otherwise the proper current circulates without passing through the 

 nerves, and consequently the contractions do not take place, or are extremely 

 feeble. These contractions- continue, generally, only for ten or fifteen mi- 

 nutes, but rarely for half an hour after preparation. 



Nobili has stated, that in arranging the frogs, so that the nerves of one 

 touch those of the other, or the muscles came into contact with muscles, no 

 contractions ensued, because, as he explained, the electro-motor elements were 

 opposed. In Matteuci's hands, however, such a result was not obtained. If 

 care be taken not to oppose to each other the nerves or muscles of symmetrical 

 parts, contraction will always ensue. 



The following is Matteucci's mode of shewing this remarkable experiment. 

 The limbs of a frog are prepared in the ordinary way ; but, in addition, the heads 

 of the thigh-bones and the ilium are completely removed, so as to leave the 

 legs connected to each other only by the nerves, through the portion of the 

 cord which is contained in the segment of the spine which remains. The 



