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and abuse with which Phrenology was treated at its first announcement, and its continued rejection by men of established reputation, whose opinions it contradicts, afford no presumption that it is untrue, for all great discoveries have met with a similar fate: Secondly, That we are really unacquainted with the mind, as an entity distinct from the body, and that it is owing to the mind not being conscious of its organs, that metaphysicians have supposed their feelings and intellectual perceptions to be emanations of pure mind, whereas they are the results of mind and its organs acting in combination. Thirdly, That the greatest anatomists and physiologists admit the brain to be the organ of the mind, and common feeling localizes the mind in the head, although it does not inform us what substance occupies the interior of the skull: Farther, That the very idea of the mind having an organ, implies that every mental act is accompanied with an affection of the organ, and vice versa; so that the true philosophy of the mind cannot be discovered without taking the influence of the organs into account at every step. Fourthly, That the analogy of the nerves of feeling and motion, of the five senses, and other parts of the body, all of which perform distinct functions by separate organs; also the successive appearance of the faculties in youth; the phenomena of partial genius, of dreaming, of partial insanity, of monomania, and of partial injuries of the brain, furnish presumptive evidence that the mind manifests a variety of faculties by means of a variety of organs, and exclude the supposition of a single power operating by a single organ. The next inquiry, therefore, naturally is, What effect does the condition of the organs produce on the states of the mind? Is it indifferent whether the organs be large or small, well or ill constituted, in health or in disease?
I submit the following facts to prove that in other departments of organised nature, size in an organ, other conditions being equal, is a measure of power in its function,
and the part on which it is ramified is merely a medium
To shew the effect of size in regard to these nerves, the
Nature has given large muscles, in order to increase their locomotive powers, and in them the nerves of motion are less. In these instances, nature curiously adds to the power of motion, by increasing the size of that part of the locomotive apparatus which may be enlarged most conveniently for the animal; but either the muscle or the nerve must be enlarged, otherwise there is no increase of power.
In regard to the external senses, it is proper to observe that every external sense is composed, first, Of an instrument or medium on which the impression is made; the eye for example; and, secondly, A nerve to conduct that impression to the mind or brain. The same law of size holds as to them; a large eye will collect more rays of light; a large ear more vibrations of sound; and large nostrils more odorous particles than small ones. This is so obvious, that it scarcely requires proof; yet, as Mr JEFFREY has ridiculed the idea, I may mention that MONRO, BLUMENBACH, SOEMMERING, CUVIER, Magendie, Georget, and a whole host of physiologists, support it. BLUMENBACH, when treating of smell, says, "While animals of the most acute smell have the nasal organs most extensively evolved, precisely the same holds in regard to some barbarous nations. For instance, in the head of a North American Indian (represented in one of his plates), the internal nostrils are of an extraordinary size," &c. And again, "The nearest to this in point of magnitude, are the internal nostrils of the Ethiopians, from among whom I have seen heads very different from each other, but each possessing a nasal organ much larger than that described by SOEMMERING. These anatomical observations accord with the accounts given by the most respectable travellers, concerning the wonderful acuteness of smell possessed by these savages."
In like manner, Dr MONRO primus, no mean authority, in treating, in his Comparative Anatomy, of the large organ of smell in the dog, says, "The sensibility (of smell) seems to be increased in proportion to the surface; and this will also be found to take place in all the other senses."
The same author states, "that the external ear in different quadrupeds is differently framed, but always calculated to the creature's manner of life; thus hares and such other animals as are daily exposed to insults from beasts of prey, have large ears directed backwards, their eyes warning them of danger before."
These observations apply to the external portion of the organs of sense. The inner parts or nerves are likewise subject to the same law of size. GEORGET, a late physiological writer, in treating of the nerves, says, "The volume of these organs bears a uniform relation, in all the different animals, to the extent and force of the sensations and movements over which they preside. Thus, the nerve of smell in the dog is larger than the five nerves of the external senses in man." The nerve of smell is small in man and in the monkey tribe; scarcely, if at all, perceptible in the dolphin; large in the dog and the horse, and altogether enormous in the whale and the skate, in which it actually exceeds in diameter the spinal marrow itself. In the mole it is of extraordinary size, while the optic nerve is very small. In the eagle the reverse is observed, the optic nerve being very large, and the olfactory small. Most of the quadrupeds excel man in the acuteness of their hearing, and accordingly it is a fact that the auditory nerve in the sheep, the cow, the horse, &c., greatly exceeds the size of the same nerve in man. In some birds of prey, which are
known to possess great sensibility of taste, the palate is found to be very copiously supplied with nervous fila
But the organ of sight affords a most interesting example of the influence of size. The office of the eye-ball is to collect the rays of light. A large eye, therefore, will take in more rays of light, or, in other words, command a greater sphere of vision, than a small one. But to give intensity or power to vision, the optic nerve is also necessary. Now, the ox placed upon the surface of the earth is of a heavy structure and ill fitted for motion, but he has a large
eye-ball which enables him to take in a large field of vision without turning; but as he does not require very keen vision to see his provender on which he almost treads, the optic nerve is not large in proportion to the eyeball. The eagle, on the other hand, by ascending to a great height in the air, enjoys a wide field of vision from its mere physical position. It looks down from a point over an extensive surface. It has no need, therefore, of a large eyeball to increase artificially its field of vision; and, accordingly, the ball of its eye is comparatively small, but it requires, from that height, to discern its prey upon the surface of the earth, and not only is the distance great, but its prey often resembles in colour the ground on which it rests. Great intensity of vision, therefore, is necessary to its existence. Accordingly, in it the optic nerve is increased to an enormous extent. Instead of forming a single membrane lining only the inner surface of the posterior chamber of the eye, as in man and animals of ordinary vision, and consequently only equalling in extent the sphere of the eye to which it belongs, the retina or nerve of vision in these quick-sighted birds of prey is found to be composed of a great number of folds, each hanging loose into the eye, and augmenting, in an extraordinary degree, not only the extent of nervous surface, but the mass of nervous matter, and giving rise to that intensity of vision which distinguishes the eagle, falcon, hawk, and similar animals. In the case of all the senses, then, the law holds, that power of function is in proportion to size of the organ, other circumstances being equal.
Let us now attend to the brain. Were I to affirm that difference of size in the brain would produce no effect on the vigour of its functions,—or that a small brain in perfect health, and of a sound constitution, is equal in functional power and efficiency to a large one in similar condition, Would the reader, after the evidence which has been laid before him of the influence of size in increasing the power of function in all other parts of the body, be dispos