Chemical Science. 183 



brought into contact, that contractions took place in the muscles of 

 the frog*. 



5. ON THE IDENTITY OF THE NERVOUS AND ELECTRIC FLUIDS. 



The following experiment is from an inaugural thesis by Dr. David, 

 of Paris: * The sciatic nerve of a rabbit was insulated and laid 

 bare, and carefully sponged ; a piece of glass was gently introduced 

 between the nerves and the muscles, while the leg of the animal 

 was bent. The sensibility of the nerve was shown by the motions 

 of the animal during the introduction of the needles, the one above 

 the other, but not touching each other. They were placed in com- 

 munication with the galvanometer : the animal was quite tranquil, 

 and the needle of the instrument at rest. By a sudden movement 

 of the rabbit, the apparatus was deranged, but the needle clearly 

 deviated and moved. The needles were again introduced ; some 

 muscular contraction succeeded, again the needle oscillated, but so 

 slightly, as not to convince the assistants. The animal, however, 

 soon made some very vigorous and repeated exertions, and there 

 was no longer any doubt of the fact, for the needle now described 

 an arc of more than two lines. The oscillations ceased with the 

 motions of the animal, and again appeared when it moved. The 

 animal was excited to make contractile efforts, by stimulating the 

 nostrils or irritating the nerve, and the needle immediately oscillated, 

 and the arc it described was great in proportion to the energy of the 

 muscular exertions which were provoked. The phenomena could, 

 in fact, be caused at will. With four needles, double the effect could 

 be produced than when two only were employed. In general, the 

 intensity of the phenomena diminished with the vigour of the 

 animal, and they were not observable after death. When two needles 

 were placed in a nerve, and two in a muscle, the oscillations were 

 barely perceptible ; when all four were introduced into a muscle, M . 

 David could obtain no deviation of the galvanometric needle. 



Other experiments demonstrated why sometimes the phenomena 

 may not arise when needles were placed in a nerve. The causes of 

 the non-occurrence of the phenomena may be either, i. Insensibi- 

 lity of the nerve, from its being strained or pressed upon in spong- 

 ing it. ii. Its too great tension over the glass placed beneath, 

 iii. Blood may cover both the nerve and needles, iv. The per- 

 fect dryness of the nerve, produced by the sponge. It is then 

 necessary to place the nerve for a moment in contact with the 

 muscles, and its power is restored. It is highly important that the 

 needles and the extremities of the threads of the galvanometer 

 should be perfectly clean. 



M. David considers these experiments sufficient, i. To prove 

 that organized beings have a special apparatus, which is destined to 



Journal des Progres des Sciences et Med., torn, ii., 1830 



