— Fan. 
20, 1870] 
MA BORE 
399 
SENSATION AND PERCEPTION 
II. 
JHE doctrine that there is a distinct organ for the 
realisation of Sensations only, apart from that for 
Perception, has been very generally taught, and has been 
insisted on by no one more strongly than by Dr. Carpenter 
in his otherwise most able and suggestive expositions of 
nervous physiology. He says:* ‘The general rule of 
action appears to be that the impressions made by ex- 
ternal objects upon the afferent nerves, when transmitted 
to the spinal cord, ascend towards the cerebrum without 
exciting any reflex movements in their course. When 
such an /fresston arrives at the sensorium,,y it excites the | 
consciousness of the individual, and thus gives rise to a 
sensation, and the change thus induced being further 
propagated from the sensory ganglia to the cerebrum, 
gives occasion to the formation of an 7dea.” And that 
Dr. Carpenter here means by the word ‘idea’ what we 
have previously spoken of as that complex intellectualised 
sensation generally called a ‘ perception,’ seems obvious 
from the following passage occurring on another page, 
where the same author says: “It is further important to 
keep in mind the distinction between the sevsations them- 
selves and the zdeas which are the immediate results of 
those sensations when they are perceived by the mind. 
The ideas relate to the cavse of the sensation or the 
object by which the impression is made” (p. 711). But 
since, in Dr. Carpenter’s view, the sensory ganglia con- 
stitute the sevsorzum, in which impressions become con- 
scious sensations; and because he naturally thinks it very 
improbable that there are two distinct organs of conscious- 
ness, he is compelled to adopt the hypothesis that the 
superficial grey matter of the cerebral hemispheres, in which 
intellectual operations are principally carried on, is not | 
itself endowed with the function of consciousness. Thus he 
assumes—as the most probable inference to be drawn 
from various kinds of evidence—“ that the sensory ganglia 
constitute the seat of consciousness not merely for impres- 
sions on the organs of sense, but also for changes in the 
cortical substance of the cerebrum; so that until the 
latter have reacted downwards upon the sensorium we 
have no consciousness either of the formation of ideas or 
of any intellectual processes of which these may be the 
subject.”+ And, although we are quite unable to agree 
with the conclusions themselves as to the absence of con- 
sciousness in connection with the activity of the cerebral 
hemispheres, and as to its presence as a functional attri- 
bute of the sensory ganglia alone, still it is sufficiently 
interesting, in a philosophical point of view, to find Dr. 
Carpenter declaring so confidently in favour of a distinct 
organ of consciousness, even altogether separate from 
those parts of the cerebral hemispheres in which what we | 
have called \ fotential knowledge is produced—meaning by 
this term what is called knowledge, so far as it can exist 
minus the attribute of consciousness. The elaboration of 
this potential knowledge is, in fact, a process the possi- | 
bility of which has been ably discussed by Dr. Carpenter | 
in the section in which he speaks of ‘unconscious cere- 
bration.” 
We must, however, briefly inquire into the reasons 
which have induced Dr. Carpenter to regard these so- 
called sensory ganglia as the seat of consciousness ; | 
though, before doing so, it will be well to draw the reader’s 
_ attention to the following considerations. As it is quite 
true that different nerves, coming from the sense organs or 
surface of the body generally, do pass through the sensory 
ganglia on their way to the higher centres in the cerebral 
hemispheres, it is obvious that the impressions made upon 
any one of these lower centres must be gwvalified to a | 
* Principles of Comparative Physiology, fifth edition, p. 707. 1854. 
+ Constituted by certain ganglionic structures at the base of the brain, in 
relation with the various sensory nerves, and usually spoken of as the 
sensory ganglia. 
t Loc. cit., p. 546. ; : 
§ See paper on ‘‘ Consciousness,” in Four. of Ment. Science, p. 512. 
certain extent, inasmuch as they are the middle terms of 
aseries, and therefore are related to their antecedents 
and to their consequents in the same way that these are 
related to one another—the antecedents being the external 
impressions, and the consequents the resulting perceptions. 
For, when an impression of a certain kind is made upon 
any given part of the surface of the body, this impression 
traverses definite nerve-fibres, in order to reach functionally 
related portions of the cerebral hemispheres, and so we 
may well suppose that the fibres, on their way, must neces- 
sarily pass through definite parts of the sensory ganglia, 
and produce, in certain of the ganglionic elements there 
situated, impressions of a definite kind. 
Thus, therefore, although we may believe that no 
| state of consciousness is aroused by this molecular action 
taking place in these lower sensory ganglia, the impressions 
made upon them may be, nevertheless, definite enough in 
kind and place to ensure a partial transference of such 
molecular movement along given and accustomed outgoing 
| motor channels; such organic possibilities of motorial 
response having been slowly built up and_elaborated, in 
past time, under the guidance of then co-existing and 
related conscious states. Thus, movements may at times 
be produced in every way similar, as regards mode of 
origin, to those automatic or reflex movements occurring 
through the intervention of the spinal cord alone ; though 
| they may be as much more complex, and apparently - 
| purposive, as these higher centres are more complex than 
| the spinal centres. And it is, we think, because the 
movements are produced by reflections from the highest 
motor centres, whose complexity renders the most purpo- 
sive movements possible, that such movements have been 
supposed to be invariably the sequences of conscious 
impressions or sewsatzons, and have hence received the 
| appellation of sezsorz-motor. This name, however, begs the 
| question in dispute—as to whether impressions reaching 
thus far would be revealed in consciousness or not ; and 
from what has been already said it will be seen that in 
the settlement of this question we must not rely too much 
upon the purposive nature of the movements as evidence 
that they are the results of conscious impressions. 
Reasonings of this kind led Pfliiger to suppose that the 
spinal cord was also a seat of consciousness. 
We quite agree with Dr. Carpenter* and others, however, 
in the opinion that the organic possibilities of executing 
all combined muscular movements of which the individual 
is capable, reside in the spinal cord and medulla, and also 
still higher in the motor centres in immediate connection 
with these so-called sensory ganglia—by virtue of definite 
| nerve connections therein established. So that all the 
facts with which we are acquainted, as he says, “tend 
strongly in favour of the view that even voluntary move- 
| ments are executed by the instrumentality of the automatic 
| apparatus, and that they differ only from the automatic or 
| instinctive in the nature of the stimulus by which they 
| are excited.” This doctrine may be aptly illustrated by 
| reference to the act of coughing, since this is an instance 
in which a complicated set of movements usually produced 
automatically may nevertheless be incited by a voluntary 
determination, When so produced, the will is directed to 
| the production of the result as a whole ; no attempt being 
| made to single out the different movements, and then to 
combine them ; so that, as Dr. Carpenter also says, “the 
will thus seems obviously to take the place of the 
laryngeal or tracheal irritation as the primum mobile of 
the series, which, in its actual performance, is as automatic 
in the latter case as in the former.” In each case, the 
same organised set of nerve connections in the higher 
motor centres (constituting the organic representatives of 
the combined muscular movements of the act of coughing) 
| are called into activity; now by a volitional incitation 
| descending from the cerebral hemispheres, and, at another 
time, as a result of an afferent stimulus reaching the 
| * Human Physiology, fifth edition, p. 516, 
