As the passing thought—the change wrought during the exercise of the intellect—may excite the centre of emotion, so this latter may exert its influence upon the general tenor of the mind, and give to all our thoughts the tinge of mirth or sadness, of' hope or despondency, as one or the other may prevail. We say of one man, that he is constitutionally morose ; of a second, that he is naturally gay and mirthful; and of a third, that he is a nervous man, and that he is never likely to be otherwise. One man allows his feelings to hurry him on to actions which his intellect condemns ; whilst another has no difficulty in keeping all his feelings in entire subjection to his judgment. " Of two indivi duals with differently constituted minds," re marks Dr. Carpenter, " one shall judge of everything through the medium of a gloomy morose temper, which, like a darkened glass, represents to his judgment the whole world in league to injure him ; and all his determina tions, being based upon this erroneous view, exhibit the indications of it in his actions, which are themselves, nevertheless, of an en tirely voluntary character. On the other hand, a person of a cheerful, benevolent disposition, looks at the world around as through a Claude Lorraine glass, seeing everything in its brightest and sunniest aspect, and, with intellectual fa culties precisely similar to those of the former individual, he will come to opposite conclu sions : because the materials which form the basis of his judgment are submitted to it in a very different form." Such examples abut-17 dantly illustrate the important share which the emotions take in the formation and develope ment of character, and how all things presented to the mind through the senses may take their hue from the prevailing state of the feelings. If a certain part of the brain be associated with emotion, it is plain that that part must be in intimate connection with the seat of change in the operations of the intellect, in order that each may affect the other; that the former may prompt the latter, or the latter excite or hold in check the former. And this association of the emotions with a certain portion of the brain explains the influence of natural temperament, and of varying states of the physical health, upon the moral and intellectual condition of individuals. We may - gather from it how necessary it is to a well-regulated mind that we should attend not to mental culture only, but to the vigour and health of the body also ; that to ensure the full developement of the mens sana we must secure the possession of the corpus sanum.
Certain diseases are evidently associated with disturbed or excited states of emotion. In such cases, the nerves most affected are those connected with the mesocepliale and medulla oblongata, denoting an excited state of these portions of the encephalon. Of these diseases the most remarkable are h,ysteria and chorea; both of which may be induced either by a cause acting primarily upon the mind, or by functional disturbance of the body, as de ranged assimilation, in persons of a certain character of constitution. In hysteria, the globus, the tendency to cry or laugh, the dis turbed breathing, the variously deranged state of the respiratory acts, all denote affection of most, if not all, the nerves coming from these segments. In chorea the frequent movements of the face and eyes, the peculiar and very characteristic mode of protruding the tongue, the impaired power of articulation, are depen dent on an altered state of that part in which the portio dura of the seventh pair, the third, fourth, and sixth, and the ninth nerves are implanted. In both diseases the principal
centml disturbance is in the mesocephale; and this may be caused either by the direct in fluence of the mind upon it, or by the propa gation of a state of irritation to it frotn some part of the periphery. Chorea, even of the most violent and general kind, is very commonly produced by sudden fright; and it is well known how frequently mental anxiety or ex citement developes the paroxysm of hysteria.
There is no part of the cerebro-spinal centre which appears to exercise such extensive sway over the movements and sensations of the body as this portion, the mesocephate, which may be regarded as the centre of emotional actions. Its influence extends upwards to the cerebral convolutions—backwards to the cerebellum— downwards to all the nerves of sensation and motion. Through its connection with the pos terior horns of the spinal grey matter, it atn excite the sensitive as well as the motor nerves of the trunk. Bence it is not to be wondered at that a highly disturbed state of this centre is capable of demnging all the sensitive as well as motor phenomena of the body and even the intellect. Hence we may explain the extm ordinary movements in hydrophobia and ge neral chorea, in both of which dismses this part of the nervous centre is doubtless affected. It has often been remarked how much more powerful are the voluntary actions when prompted by some strong emotion, than when excited only by an effort of the will. nage, or despair, is able to magnify the power of the muscles to an incalculable degree. This may be due to the increased stimulus derived from the influence of the centre of emotion being conjoined with that of the centre of volition.
The intimate connection of the olivary co lumns with the grey matter of the cord, and through that with all the roots of the spinal nerves, illustrates the power of emotional changes upon the organic processes. How often does the state of the feelings influence the quantity and quality of the secretions, no doubt through the power of the nerves over the capillary circulation ! Blushing is pro duced through an affection of the mind, acting priinarily on the centre of emotion, and through it on the nerves, which are distributed to the capillary vessels of the skin of the face.
The sexual passion must be ranked among the mental emotions. Like them, it may be excited and ministered to by a certain line of thought, or by particular physical states of the sexual organs. It seems, therefore, more cor rect to refer this emotion to the comnaon centre of all, than to a special organ—according to Gall's theory; and it may be remarked, that grmt developement of this part of the brain is just as likely to produce grmt width of cranium in the occipital region as a large cerebellum.
Of the junctions of the cercbellum.—All ana tom ists are agreed in admitting, in the whole vertebrate series, (the amphioxus, perhaps, ex cepted,") the existence of a portion of the en cephalon which is analogous to the cerebellum. This extensive existence of such an organ indi cates its great physiological importance, as a special element of the encephalon. The ce rebellum exhibits much diflerence both as re gards size and complexity of structure in the different classes ; and although, upon the whole, it increases in its development in the same ratio as the hemispheric lobes, it exhibits no constant relation of size to those parts.