DR. MARSHALL HALL. 
623 
or motor; and that the ganglionic are the centres of incident 
and reflex nerves, and of the reflex actions. “ It remains, ” says 
the Doctor, “ to be ascertained whether the sentient nerves be- 
long to the ganglionic columns: but this seems most probable. ” 
Sir Charles Bell, besides the nerves of vision, smell, and hear- 
ing, made four systems of the nerves, — of sensation , voluntary 
motion , respiratory motion , and the sympathetic system. Dr. 
M. Hall, in arranging all under three heads — the cerebral, true 
spinal, and ganglionic systems — includes Sir C. Bell’s u respira- 
tory” system in the true spinal ; and thus interprets the modus 
operandi and nervous influence of the entire respiratory appara- 
tus : — 
I. Excitors. II. Centre. III. The Motors. 
1. The Trifacial. d 1. The Spinal Accessory. 
Respiration is a mixed function ; i. e. it is either cerebral or 
true spinal , either under the influence of the will, or else, uncon- 
sciously to the animal, carried on by the excito-motory system. 
Ordinary inspirations are neither, according to Wilson Philip 
and Mayo, acts of volition or consciousness ; nor, according to 
Bostock, Wilson Philip, and Brachet, acts dependent upon the 
pneumogastric nerves as nerves of sensation ; nor, according to 
Legallois, Sir C. Bell, Flourens, and Muller, acts dependent 
upon the medulla oblongata as their primum mobile ; but are 
excito-motory acts, excited by particular nerves, but still regu- 
lated and modified by volition. The first inspiration in the new- 
born infant is probably excite 1 through the medium of the fifth 
and spinal nerves conjointly with the contact of the atmosphere: 
in after-life, the exciting cause of inspiration appears to be the 
presence of carbonic acid within the air-cells of the lungs, in 
contact with the fibrillae of the pneumo-gastric nerves. 
If carbonic acid in a pure form be applied to the larynx, or if 
the rima glottidis be tickled with a feather, the glottis instantly 
closes firmly ; and these effects may be produced in an animal 
deprived of the cerebrum. The explanation is this : the excitor 
nerve, the superior laryngeal, conveys the excitation to the centre , 
the medulla oblongata; whence it is reflected along the motor 
nerve, the recurrent, to the larynx, producing the closure of it. 
[The name of the author of this beautiful sketch of the Excito- 
motory Nervous System the Editor is not permitted at present 
to divulge; but the period, we trust, is not far distant when 
our readers will know all about it. — Y.l 
2. The Pneumo-gastric. 
3. The Spinal. 
2. The Intercostal. 
3. The Diaphragmatic. 
4. The Posterior Lower Spinal, 
&c. 
