DEPRESSOR-NERVE. 229 



Depivssor-Newe. An important reflex action operating 

 upon the circulation through branches of the pneumogastrics 

 has lately been described by Cyon and Ludwig, in a memoir 

 which received the prize for Experimental Physiology from 

 the French Academy of Sciences, in 1867. 1 The experi- 

 ments on which this memoir is based are exceedingly clear 

 and satisfactory, and afford, perhaps, the only positive expla- 

 nation we have of reflex action upon the heart. 'The sub- 

 stance of these observations is briefly as follows : 2 



In the rabbit is a nerve arising by two roots, one coming 

 from the trunk of the pneumogastric and the other from its 

 superior laryngeal branch, passing then toward the carotid 

 artery and taking its course down the neck by the side of 

 the sympathetic as far as the thorax. " In the chest, it joins 

 with sympathetic filaments to pass with them to the heart, 

 by little branches between the origin of the aorta and the 

 pulmonary artery. 



This nerve can be completely isolated in the neck from 

 the sympathetic and the trunk of the pneumogastric. If it 

 be divided m this situation, after the irritation produced 

 by the operation has subsided, very distinct and important 

 modifications in the circulation may be produced by its gal- 

 vanization. 



In the first place, it was noted in all the experiments, 

 that galvanization of the peripheral extremities produced no 

 change, either in the number of the pulsations of the heart 

 or in the pressure of blood in the vascular system ; which 



noted by Traube. (TRAUBE, Zur Physiologic des Nervus vagus. Gesammdte 

 Bdtrdge, Berlin, 1871, Bd. L, S. 184.) 



1 BERNARD, Rapport sur un memoire de M. E. CYOX, intitule : de V action re- 

 flexe d>un des nerfs sensibles du cceur. Journal de Tanatomie, Paris, 1868, tome 

 v., p. 337. 



2 CYON ET LUDTTIG, Action reflexe d"*un des nerfs sensibles du cceur sur les 

 nerfs vaso-moteurs. Journal de V anatomic, Paris, 1867, tome iv., p. 472, et scg. 



Cyon has lately found in the horse, nerves, in their anatomical and physio- 

 logical relations, closely resembling the "depressor-nerves" which he first de- 

 scribed in the rabbit (British and Foreign Medico- Chirurgical Review, London, 

 1871, Xo. xcvi., p. 540). 



