72 Linnaran Society, 



branches des nerfs et qui n'agit Jamais en arriere.*' In Dr. Hall's 

 experiments the influence first pursued 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 partaking 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 

 first case the agency of volition is alone removed, and the respira- 

 tion continues through the influence of the eighth pair; in the 

 second, that of the eighth pair is removed, and the respiration con- 

 tinues as a function of volition ; but in the third, both influences are 

 destroj'^ed at once, and with them the mixed or double function. 



The same mixed or double character belongs to the other parts of 

 the reflex function, as that of the larynx, the sphincters, the eja- 

 culators. All the organs of the reflex function are also alike im- 

 pressed through the medium of the mental aff^ections or passions. 



The course of the influence which constitutes the reflex function 

 must be divided into the incident, or that into the medulla, and the 

 reflected, or that from the medulla. The nerves which conduct the 

 incident impression have, hitherto, received no designation ; the 

 others constitute a part of the system of muscular nerves. To the 

 former class belong nerves which doubtless supply the larynx with 

 its impressibility by carbonic acid, &c., &c., and hitherto unde- 

 scribed, untraced ; to the latter, the superior and inferior laryngeals : 

 to the former belong the fifth, in the nostrils, in the face, — the 

 eighth in the lungs, &c. ; to the latter, the respiratory nerves : to 

 the former, nerves hitherto undescribed of the sphincters, ejacula- 

 tors, &c. ; to the latter, the muscular nerves supplying these parts. 



The whole constitutes the subject of an investigation in which 

 Dr. HaU has been for some time engaged. 



LINN^EAN SOCIETY. 



Nov. 4-. — Read descriptions of some additional species of the 

 Dipterous genus Diopsis, by John O. Westwood, Esq., F.L.S. j and 



