PHYSIOLOGY OF THE NERVOUS SYSTEM. 
deglutition are, to a great extent, of the physi- 
cal kind, being excited by impressions propa- 
gated from the periphery. In those of respira- 
tion, the ordinary exciting cause is probably, 
as Dr. Hall suggested, due to the chemical 
changes in the respired air which are effected 
in the lungs. These movements may be, toa 
certain extent, contrelled by the will; but every 
one is conscious, from his own sensations, that 
after a time the physical stimulus is capable of 
conquering the restraining influence of the 
mind ; a striking example of a mental stimu- 
lus giving way to a physical one, and illustra- 
tive of the doctrine that the same fibres 
are affected by both stimuli. The excitation 
of the medulla oblongata in respiration does 
not, however, depend solely upon the pul- 
monary nerves. Those of the skin are ca- 
pable of exciting it, either directly as the fifth 
ir, or through the spinal cord, as is proved 
y the inspirations which are instantly excited 
by suddenly dashing cold water on the face or 
trunk. 
In deglutition, the exciting cause is the sti- 
mulus of contact applied to the mucous mem- 
brane of the fauces. So highly sensitive is the 
mucous membrane in this situation, that the 
slightest touch of it with a feather is sufficient 
to produce contraction of the muscles of deglu- 
tition, which the will is scarcely able to con- 
trol. Without this stimulus, it is doubtful 
whether these muscles would obey the will 
alone, and it seems probable that this part of 
the act.of deglutition must be regarded as one 
of those actions referred to at a former page, 
which require a double stimulus, both mental 
and physical, for their full performance. 
The medulla oblongata and its continuations 
in the mesocephale appear to be the centre of 
those actions which are influenced by emotion. 
The common excitement of movements of de- 
glutition or respiration, or of sensations referred 
to the throat, under the influence of emotion, 
evidently points to this part of the cerebro- 
spinal centre as being very prone to obey such 
impulses; and as the nerves of pure sense, 
especially the optic and auditory, are very 
commonly the channels of sensitive impressions 
well calculated to arouse the feelings, it seems 
highly probable that the centre of such actions 
should be contiguous to the origin of these 
nerves. This office may be assigned to that 
Tegion of the mesocephale which is in the 
Vicinity of the quadrigeminal tubercles. It is 
not a little remarkable that the nerves which 
arise from this and the neighbouring parts are 
very readily influenced by emotions. Thus, 
the third and fourth pairs of nerves regulate 
the principal movements of the eyeballs, those 
especially which most quickly betray emotional 
excitement; and the portio dura of the se- 
venth pair, the motor nerve of the face, is the 
medium through which changes of the counte- 
hance are effected. It may be added, that the 
centre of emotional actions ought to be so situ- 
| \ated that it might readily communicate with 
_ \the centres of all the voluntary actions of the 
_|body, and with the immediate seat of the 
_\intellectual operations, as well as with the 
B\ (VOL. 111. 
722. 
nerves of pure sense; and no part possesses 
these relations so completely as that now under 
examination. 
In those diseases which mental emotion is 
apt to give rise to, many of the symptoms are 
referable to affection of the medulla oblongata. 
In hysteria, the globus, or peculiar sense of 
suffocation or constriction about the fauces; in 
chorea, the difficulty of deglutition, the pecu- 
liar movement of the tongue, the excited state 
of the countenance, the difficulty of articula- 
tion, may be attributed to the exalted polarity 
of the centre of emotional actions. In hydro- 
phobia this part is probably always affected, 
and frequently so in tetanus. 
Certain gangliform bodies are connected with 
the upward continuations of the medulla ob- 
longata, both in the brain and in the mesoce- 
hale, which doubtless have proper functions. 
hese are the corpora striata, optic thalami, 
and quadrigeminal bodies. 
Corpora striata.—The anatomy of the cor- 
pora striata and optic thalami, while it denotes 
a very intimate union between them, also shows 
so manifest a difference in their structural cha- 
racters, that it cannot be doubted that they 
perform essentially different functions. In the 
corpora striata the fibrous matter is arranged 
in distinct fascicles of various sizes, many, 
if not all of which, form a special connection 
with its vesicular matter. In the optic thala- 
mi, on the other hand, the fibrous matter forms 
a very intricate interlacement, which is equally 
complicated at every part. Innumerable fibres 
pass from one to the other, and both are con- 
nected to the hemispheres by extensive radia- 
tions of fibrous matter. The corpora striata, 
however, are connected chiefly, if not solely, 
with the inferior fibrous layer of each crus 
cerebri; whilst the optic thalami are continuous 
with the superior part of each crus, which is 
situate above the locus niger. 
It will be observed, then, that while these 
bodies possess, as a principal character in com- 
mon, an extensive connection with the convo- 
luted surface of the brain, they are, in the most 
marked way, connected inferiorly with separate 
and distinct portions of the medulla oblongata; 
the corpora striata with the inferior fibrous 
planes of the crura cerebri and their continua- 
tions, the anterior pyramids; and the optic 
thalami with the olivary columns, the central 
and probably fundamental portions of the me- 
dulla oblongata. This anatomical fact must 
be taken as an additional indication that these 
gangliform bodies perform separate functions. 
Now, it may be inferred, from their con- 
nections with nerves chiefly of a sensitive kind, 
that the olivary columns, and the optic thalami, 
which are continuous with them, are chiefly 
concerned in the reception of sensitive impres- 
sions, which may principally have reference 
merely to informing the mind (so to speak), or 
partly to the excitation of motion, as in deglu- 
tition, respiration, &c. The posterior horns of 
the grey matter of the cord, either by their 
direct continuity with the olivary columns, or 
their union with these columns through com- 
missural fibres, become part and parcel of a 
22 KEREER 
