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FUNCTIONS OF THE CEREBELLUM AND CEREBRUM. 385

tary power over its individual muscles; but it could not combine their actions for any general movement of the body. The reflex movements, such as those of respiration, remained unimpaired. When an animal in this state was laid on its back, it could not recover its former posture; but it moved its limbs or fluttered its wings, and evidently was not in a state of stupor. When placed in the erect position, it staggered and fell like a drunken man; not, however, without making efforts to maintain its balance.-Phrenologists, who attribute a different function to the Cerebellum, have attempted to put aside these results, on the ground that the severity of the operation was alone sufficient to produce them; but (as we have already seen, § 465) after a much more severe operation—the removal of the Cerebral Hemispheres, the Cerebellum being left untouched-the animal could stand, walk, fly, maintain its balance, and recover it when disturbed.

482. The motions of the body in the Invertebrated classes, being simple in their nature, and probably all of a reflex character (§ 442), do not require a Cerebellum; and we do not find in them any nervous mass which clearly represents this organ.

Functions of the Cerebrum.-Intelligence and Will.

483. From the facts already stated, it is tolerably clear that the Cerebrum is the organ by which we reason upon the ideas that are excited by sensations,-by which we judge and decide upon our course of action, and by which we put that decision into practice, by issuing a mandate (as it were), which, being conveyed by the nervous trunks proceeding from the brain to the muscles, excites the latter to contract. It is a common, but entirely erroneous idea, that Reason or Intelligence is peculiar to Man; and that the actions of the lower classes of Animals are entirely due to Instinct. There can be no doubt, however, that reasoning processes exactly resembling those of Man are performed by many Mammals, such as the Dog, the Horse, and the Elephant; and it is probable that although we are best acquainted with these animals, on account of their tendency to associate with Man, there are others which have powers yet higher. We must admit that an animal reasons, when it profits by experience, and obviously adapts its actions to the ends it desires to gain,

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386 SUPERIOR INTELLIGENCE OF HIGHER VERTEBRATA.

especially when it departs from its natural instincts to do this. Such is continually the case with the animals just mentioned, as will appear from some striking examples to be mentioned hereafter (Chap. XIV.). We perceive the presence of Intelligence also in the differences of character which we encounter among the various individuals of the same species; thus every one knows that there are stupid Dogs and clever Dogs, ill-tempered Dogs and good-tempered Dogs, as there are stupid Men and clever Men, ill-tempered Men and goodtempered Men. But no one could distinguish between a stupid Bee and a clever Bee, or between a good-tempered Wasp and an ill-tempered Wasp; simply because all the actions of these animals are prompted by an unvarying instinct.

484. Among Birds, too, there are many manifestations of Intelligence, which constitute a remarkable distinction between their actions and those of Insects; though the instinctive tendencies of the two classes bear a close correspondence with each other. Their mode of life is nearly the same, so that Birds may be called the Insects of the Vertebrated series, whilst Insects may be regarded as the Birds of the Articulated; and there are several curious points of analogy in the structure of their bodies. The usual arts which Birds exhibit in the construction of their habitations, in procuring their food, and in escaping from danger, must be regarded (like those of Insects) as instinctive; on account of the uniformity with which they are practised by different individuals of the same species, and the perfection with which they are exercised on the very first occasion, independently of all experience. But in the adaptation of their operations to particular circumstances, Birds display a variety and fertility of resource far surpassing that which is manifested by Insects; -as for instance, when they make trial of several means, and select that one which best answers the purpose; or when they make an obvious improvement from year to year in the comforts of their dwelling; or when they are influenced in the choice of a situation by peculiar conditions, such as in a state of nature can scarcely be supposed to affect them. All these are obvious indications of an Intelligence which Insects do not possess; that which is most wonderful in the actions of the latter (and there are none more wonderful) being the same in all the individuals of one species, being uninfluenced

LOW INTELLIGENCE OF REPTILES AND FISHES.

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by education, and being performed under the direction of an Intelligence much higher than the boasted reasoning power of Man.

485. In the classes of REPTILES and FISHES, the manifestations of Intelligence are so slight as to be scarcely distinguishable. We find them capable of such an amount of education as enables them to recognise individuals from whom they have been accustomed to receive food; but they seem to have very little further power of profiting by experience; and we do not find that individuals ever shape-out for themselves a new course which can be regarded as purely rational. This very low grade of Intelligence obviously corresponds with the very rudimentary development of the Cerebrum in these classes (§§ 453, 454).

The contrast between Instinct and Intelligence will be more fully displayed in a future Chapter; in which also a general account will be given of the Mental Operations to which the Cerebrum of Man is subservient.

CHAPTER XI.

ON SENSATION, AND THE ORGANS OF THE SENSES.

486. ALL save the very lowest kinds of Animals possess, there is good reason to believe, a consciousness of their own existence, first derived from a feeling of some of the changes taking place within themselves; and also a greater or less amount of sensibility to the condition of external things. How far any such endowment can be possessed by creatures which are destitute of a nervous system, and which are little else than particles of animated jelly, may be questioned. But there can be no reasonable doubt that where a nervous system exists, whatever consciousness any Animal may possess of that which is taking place within or around itself, is all derived from impressions made upon the extremities of certain of its nervous fibres; which, being conveyed by them to the central sensorium, are there felt (§ 430). Of the mode in which the impression, hitherto a change of a material character, is there made to act upon the mind, we are absolutely ignorant; we only know the fact. Hence, although we com

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SENSATION IN GENERAL.

monly refer our various sensations to the parts at which the impressions are made,-as, for instance, when we say that we have a pain in the hand, or an ache in the leg,—we really use incorrect language; for, though we may refer our sensations to the points where the impression was made on the nerve, they are really felt in the brain. This is evident from two facts; first, that if the nervous communication of the part with the brain be interrupted, no impressions, however violent, can make themselves felt; and, second, that if the trunk of the nerve be irritated or pinched anywhere in its course, the pain which is felt is referred, not to the point injured, but to the surface to which these nerves are distributed. Hence the well-known fact that, for some time after the amputation of a limb, the patient feels pains which he refers to the fingers or toes that have been removed; this continues until the irritation of the cut extremities of the nervous trunks has subsided.

487. Among the lower tribes of Animals, it would seem probable that there is no other kind of sensibility than that which is termed general or common, and which exists, in a greater or less degree, in almost every part of the bodies of the higher. It is by this that we feel those impressions, made upon our bodies by the objects around us, or by actions taking place within, which produce the various modifications of pain, the sense of contact or resistance, the sense of variations of temperature, and others of a similar character. From what was formerly stated (§ 63) of the dependence of impressions made on the sensory nerves upon the action of the blood-vessels, it is obvious that no parts destitute of the latter can receive such impressions, or (in common language) can possess sensibility. Accordingly we find that the hair, nails, teeth, tendons, ligaments, fibrous membranes, cartilages, and bones, whose substance either contains no vessels, or but very few, are either completely incapable of receiving painful impressions, or have but very dull sensibility to them. On the other hand, the skin and other parts which usually receive such impressions, are extremely vascular; and it is interesting to observe that some of the tissues just mentioned, when new vessels form in them in consequence of diseased action, become acutely sensible. It does not necessarily follow, however, that parts should be sensible in a degree proportional to

NERVES OF SPECIAL SENSIBILITY.

389 the amount of blood they contain; since this blood may be sent to them for other purposes. Thus, it is a condition necessary to the action of Muscles, that they should be copiously supplied with blood (§ 591); but they are not acutely sensible: and Glands, also, the substance of which has very little sensibility, receive a large amount of blood for their peculiar purposes.

488. But besides the general or common sensibility which is diffused over the greater part of the body of most animals, there are certain parts which are endowed with the property of receiving impressions of a peculiar or special kind, such as sounds or odours, which would have no influence upon the rest; and the sensations which these impressions excite, being of a kind very different from those already mentioned, arouse ideas in our minds such as we should never have formed without them. Thus, although we can gain a knowledge of the shape and position of objects by the touch, we could form no notion of their colour without sight, of their sounds without hearing, or of their odours without smell.

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489. The nerves which convey these special impressions are not able to receive those of a common” kind: thus, the Eye, however well fitted for seeing, would not feel the touch of the finger, if it were not supplied with branches from the 5th pair, as well as by the optic nerve. Nor can the different nerves of special sensation be affected by impressions that are adapted to operate on others: thus, the ear cannot distinguish the slightest difference between a luminous and a dark object; nor could the eye distinguish a sounding body from a silent one, except by seeing its vibrations. But Electricity possesses the remarkable power, when transmitted along the several nerves of special sense, of exciting the sensations peculiar to each; and thus, by proper management, this single agent may be made to produce flashes of light, distinct sounds, a phosphoric odour, a peculiar taste, and a pricking feeling, in the same individual at one time. The inference which might hence be drawn-that Electricity and Nervous agency are identical-is nevertheless premature, as will be shown hereafter (§ 585).

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