CHAP. XI.] FUNCTIONS OF THE ENCEPHALON. 357 



states of emotion. In such cases, the nerves most affected are those 

 connected with the mesocephale and medulla oblongata, denoting an 

 excited state of those portions of the encephaloii. Of these diseases 

 the most remarkable are hysteria 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 deranged assimilation, in 

 persons of a certain character of constitution. In hysteria, the 

 globus, the tendency to cry or laugh, the disturbed breathing, the 

 variously deranged state of the respiratory acts, all denote affection 

 of most, if not all, the nerves coming from those 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 dependent 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 central disturbance is in the mesocephale ; and that 

 may be caused either by the direct influence of the mind upon it, 

 or by the propagation of a state of irritation to it from 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 excitement develops 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 mesocephale, which we regard 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 connexion 

 with the posterior horns of the spinal gray matter, it can excite the 

 sensitive as well as the motor nerves of the trunk. Hence it is not 

 to be wondered at that a highly disturbed state of this centre is 

 capable of deranging all the sensitive as well as motor phenomena 

 of the body, and even the intellect. Hence we may explain the 

 extraordinary movements in hydrophobia and general chorea, m 

 both of which diseases 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. Rage, 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. 



