Chemical Agents on the Nervous System, 33 



inter-vertebral spaces to that integument which, the head 

 being removed, could only act in their capacity of incident 

 nerves of the spinal system. Unfortunately these nerves, 

 the largest of the kind, were still of small dimensions ; they 

 are also speedily desiccated, if exposed so as to stretch in 

 their denuded state through a portion of atmospheric air. 



The results of our researches are given in the following 

 detail of experiments : — 



Ex, 10. We removed the head and then divided the inte- 

 guments in two parallel lines, about half an inch asunder 

 along the spine; the intervening portion of integuments being 

 detached all round and raised, the cutaneous nerves are, as 

 I have stated, seen passing to it in pairs proceeding from the 

 spinal marrow. 



If when thus detached, this integument is irritated by the 

 forceps, the brain being removed, distinct reflex actions are 

 observed ; they are incident excito-motor nerves. 



We now raised this portion of integument on the zinc por- 

 tion of the Voltaic arc of zinc and silver, the silver being re- 

 tained in contact with the lateral part of the animal ; the 

 current proceeding in the incident direction, therefore, 

 through the nerves, no movements were observed on break- 

 ing the circuit. 



Ex. 11. In another experiment we prepared the frog in the 

 same manner, and placed the platinum wire from the silver 

 end of the Voltaic *' couronne de tasses" under the integu- 

 ments, and the other underneath the abdomen, the current 

 pursuing the same incident course as before ; very slight 

 movements were observed on completing the circuit, but 

 none on breaking it, and no tetanoid phenomenon could be 

 produced. 



Ex, 12. We removed the head, and, by means of longitu- 

 dinal and transverse incisions, raised the integuments still 

 attached by their nerves, placing them over the wire proceed- 

 ing from the zinc end of the battery of 50 plates, one inch 

 square of copper and zinc, whilst the copper wire was placed 

 in contact with the muscles of the dorsal region, the Voltaic 

 influence pursuing, in the nerves, a direction contrary to the 

 incident. On completing the circuit, slight movements of the 



VOL. XLVI. NO. XCI. — JAN. 1849. C 



