754 OF THE FUNCTIONS OF THE NERVOUS SYSTEM. 



case it is usually found that the convulsions are on the paralyzed side of the body 

 the effect of the lesion, both of the Cerebrum and of the Corpora Quadrige- 

 mina, being propagated to the opposite side, by the decussation of the Pyramids. 

 Where, as not unfrequently happens, there is paralysis of one side, accompanying 

 convulsions on the other, it is commonly the result of a lesion affecting the base 

 of the Brain and Medulla Oblongata, on the side on which the convulsions take 

 place ; here the effect of the lesion has to cross from the Brain, whilst its influence 

 on the Medulla Oblongata is shown on the same side. Many anomalies present 

 themselves, however, which are by no means easy of explanation, in the present 

 state of our knowledge. The disturbance of the Cerebral functions, occasioned 

 by those changes in its nutrition which are commonly included under the general 

 term of Inflammation, presents a marked diversity of character, according to the 

 part it affects. Thus it is well known that the delirium of excitement is usually 

 a symptom of inflammation of the cortical substance, or of the membranes of the 

 hemispheres. This is exactly what might be anticipated from the foregoing 

 premises, since this condition is a perversion of the ordinary mental operations, 

 which are dependent upon the instrumentality of the vesicular matter : and it is 

 evidently impossible for the membranes to be affected with inflammation, without 

 the nutrition of this substance being impaired, since it derives all its vessels 

 directly from them. On the other hand, inflammation of the fibrous portion of 

 the Cerebrum is usually attended rather with a state of torpor, than with excite- 

 ment ; and with diminished power of the will over the muscles. It is stated 

 by Foville, that in acute cases of Insanity, he has usually found the cortical 

 substance intensely red, but without adhesion to the membranes ; whilst in 

 chronic cases, it is indurated and adherent : but where the insanity has been 

 complicated with Paralysis, he has usually found the medullary portion indu- 

 rated and congested. 



786. The general result of such investigations is, that the Cerebrum is the 

 instrument of all those psychical operations, which we include under the general 

 term Intellectual, whilst it also affords, in part at least, the instrumental condi- 

 tions of Emotional states (using this term in its widest sense) ; and that all those 

 muscular movements which result from voluntary determinations, or which are 

 directly consequent upon emotional excitement, have their origin in its vesicular 

 substance, though the motor impulse is immediately furnished by the Automatic 

 apparatus, upon which the Cerebrum plays ( 757). All the operations of the 

 Mind are originally dependent upon the reception of Sensations. If it were 

 possible for a Human being to come into the world, with a Brain perfectly pre- 

 pared to be the instrument of psychical operations, but with all the inlets to 

 sensation closed, we have every reason to believe that the Mind would remain 

 dormant, like a seed buried deep in the earth. The attentive study of cases, in 

 which there is congenital deficiency of one or more sensations, makes it evident 

 that the Mind is utterly incapable of forming any definite ideas in regard to 

 those properties of objects of which those particular sensations are adapted to 

 take cognizance. Thus the man who is born blind can form no conception of 

 color ; nor the congenitally deaf, of musical tones. And in those lamentable 

 cases, in which the sense of touch is the only one through which ideas can be 

 introduced, it is evident that the mental operations must remain of the simplest 

 and most limited character, if the utmost attention be not given, by a judicious 

 instructor, to the development of the intellectual faculties, and the cultivation 

 of the moral feelings, through that restricted class of ideas which there is a pos- 

 sibility of exciting. The activity of the Mind, then, is just as much the result 

 of its consciousness of external impressions, by which its faculties are called into 

 play, as the Life of the body is dependent upon the appropriation of nutrient 

 materials, and the constant influence of external forces. But there is this dif- 

 ference between the two cases that whilst the Body continually requires new 



