95 



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

 eighth, Dr. Hali associates other spinal nerves. He considers re- 

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

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

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

 pressions carried to and from the medulla oblongata and^medulla 

 spinalis. Soma illustrations of this function were given by Dr. Hali 

 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. Mūller in his Paper entitled " Nouvelles Expėri- 

 ences sur l'effet que produit l'Irritation mėcanique et galvaniąue sur 

 les racines des nerfs spinaux ; par Jean Mūller, Professeur a l'Uni- 

 versitė de Bonn," and published in the ' Annales 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 on tonique, qui ne peuvent 

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

 ritės par l'action galvanique ou mėcanique, et qui ne eonduisent le 

 courant galvanique que passivement, comme toutes les parties moUes 

 humides ; qu'il y a en revanche des nerfs moteurs ou toniąues (nervi 

 motorii seu tonici) qui montrent k chaque irritation mediate ou im- 

 mėdiate leur force tonique, ąui agit toujours dans la direction des 

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

 experiments the influence first pursued a backward course to the 

 spinal marrow, being afterwards reflected upon the museles. 



Dr. HaU 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 mLxed, or partaJdng of 

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

 following facts : 



1 . If the cerehrum 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 tvro sources of the mixed or double function 

 being both cut ofF, the function ceases. 



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

 apparently contradictory facts, — that the medulla oblongata fdone, 

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

 nerves themselves, may be di%ided, -vvithout 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 



