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tributed to external as well as internal surfaces. With the fifth and 

 eighth. Dr. Hall associates other spinal nerves. He considers re- 

 spiration as a part of a general function of the nervous system, 

 wliich presides over the larynx, pharynx, sphincters, ejaculators, &c., 

 to which he has given the name of reflex, from its consisting of im- 

 pressions carried to and from the medulla oblongata and^medulla 

 spinalis. Some illustrations of this function were given by Dr. Hall 

 at the Meeting of the Committee of Science and Correspondence 

 on November 27, 1832, (Proceedings, Part ii. p. 190,) and fur- 

 ther illustrations of it have formed the subject of a Paper by him, 

 which has since been published in the ' Philosophical Transactions'. 

 The experiments shown on the present occasion demonstrate the 

 existence of a series of physiological facts at variance with the law 

 laid down by M. Miiller in his Paper entitled " Nouvelles Experi- 

 ences sur I'eflFet que produit I'lrritation mecanique et galvanique sur 

 les racines des nerfs spinaux ; par Jean Midler, Professeur a I'Uni- 

 versite de Bonn," and published in the ' Annates des Sciences Na- 

 turelles, ' tom. xxiii. (1831), p. 95, viz. " II suit encore qu'il y a 

 des nerfs qui n'ont point de force motrice ou tonique, qui ne peuvent 

 jamais occasionner des mouvemens par eux-memes, qu'ils soient ir- 

 rites par Taction galvanique ou mecanique, et qui ne conduisent le 

 courant galvanique que passivement, comme toutes les parties molles 

 humides ; qu'il y a en revanche des nerfs moteurs ou toniques {nervi 

 motorii sen tonici) qui montrent ci chaque irritation mediate ou im- 

 mediate lem: force tonique, qui agit toujours dans la direction des 

 branches des nerfs et qui n'agit jamais en arriere." In Dr. Hall's 

 experiments the influence first piirsued a backward course to the 

 spinal marrow, being afterwards reflected upon the muscles. 



Dr. Hall next observed, in regard to respiration, that, whilst Sir 

 Charles Bell is contending that it is involuntary, and Mr. Mayo that 

 it is voluntary, the old doctrine of its being mixed, or pEirtaking of 

 both properties, is the true one. He founded this view upon the 

 following facts : 



1 . If the cerebrum be removed, respiration continues as an invo- 

 luntary function through the agency of the eighth pair of nerves ; 



2. If the eighth pair be divided, respiration equally continues, 

 but as an act of volition ; but 



3. If the cerebrum be first removed, and the eighth pair be then di- 

 vided, respiration ceases on the instant. Volition is first removed 

 with the cerebrum; the influence of the eighth pair is then removed 

 by its division. The two sources of the mixed or double function 

 being both cut off, the function ceases. 



Dr. Hall explains and reconciles in this manner the difficult and 

 apparently contradictory facts, — that the medulla oblongata alone, 

 above the origin of the eighth pair of nerves, or the eighth pair of 

 nerves themselves, may be divided, without arresting the respira- 

 tion ; but that the medulla oblongata cannot be divided at the origin 

 of these nerves without arresting the respiration instantly. In the 



