704 FUNCTIONS OF THE CEREBRO -SPIN AL NERVOUS SYSTEM. 



to be noticed in all diseases of the Encephalon. The partial or entire 

 absence of the commissure from congenital malformation reducing the Cere- 

 brum (in this respect) at least, to the level of that of the Marsupial Quadru- 

 ped or of the Bird is by uo means an unfrequent cause of deficient intellectual 

 power. In an interesting case recorded by Mr. Paget, 1 in which the middle 

 portion of the fornix and the whole of the septum lucidum were absent, 

 with a very thin and short corpus callosum, the subject had been a servant 

 girl, and had during life betrayed a peculiar want of forethought and power 

 of judging of the probable result of things, but her memory was good, and 

 she possessed an ordinary amount of knowledge. A similar case has been 

 recorded by Mitchell Henry. 2 The mental deficiencies in this and in most 

 of the few other cases of which the details have been recorded, seem to have 

 been of the same order; and this is exactly what might have been antici- 

 pated ; since the deprivation of these parts takes away that which is most 

 characteristic of the Cerebrum of Man and of the higher Mammalia ; their 

 intellectual operations being peculiarly distinguished by that application of 

 past experience to the prediction of the future, which constitutes one of the 

 highest efforts of intelligence. A sudden lesion, that may be so trifling as 

 to escape observation unless this be very carefully conducted, will occasion 

 very severe symptoms ; whilst a chronic disease may gradually extend itself, 

 without any external manifestation. It will usually be found that sudden 

 paralysis, of which the seat is in the Brain, results from some slight effusion 

 of blood in the substance or in the neighborhood of the Corpora Striata ; 

 whilst, if it follows disorder of long standing, a much greater amount of 

 lesion commonly presents itself., In either case, the paralysis occurs in the 

 opposite side of the body, as we should expect from the decussation of the 

 Pyramids; but it may occur either on the same, or on the opposite side of 

 the face, the cause of which has already been explained. The disturbance 

 of the Cerebral functions occasioned by those changes in its nutrition which 

 are commonly included under the general term 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 inflam- 

 mation 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 evi- 

 dently impossible for the membranes to be affected with inflammation, with- 

 out 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 excitement; 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 indurated and congested. 



569. The numerous and interesting observations which have been made 



large proportion of the cases examined after death, disease has been found 

 in the posterior part of the third or inferior frontal convolution of the left 

 hemisphere ; hence the conclusion has been drawn that the faculty of lau- 



1 Mi'd.-Chir. Trans., vol. xxiv. 2 Op. cit., vol. xxxi. 



3 See Aphasia, Agniphia, etc., in the Year-Books of the New Sydenham Society. 



