FUNCTIONS OF THE CEREBRUM. 211 



commonly found in persons of what has been termed the phlegmatic tempera- 

 ment, in whom the general processes of life seem in a torpid and indolent 

 state ; whilst small brains and great activity betoken what are known as the 

 sanguine and nervous temperaments. These distinctions come to be very 

 important, where we proceed further in our inquiries, and attempt to deter- 

 mine the particular modes of development of the Brain, which coincide with 

 certain manifestations of the mind. 



286. Having now inquired into the evidence of the general functions of the 

 Cerebrum, which may be derived from examination of its comparative deve- 

 lopment, we proceed to our other sources of information Experiment and 

 Pathological phenomena. The effects of the entire removal of the Hemi- 

 spheres have been already described ( 264). In these and similar experi- 

 ments, it has been constantly remarked that injuries of the Cerebral substance 

 do not occasion signs of pain, and that they do not give rise to any convulsive 

 movements. Even the Thalami and Corpora Striata may be wounded, with- 

 out the excitement of convulsions ; but if the incisions involve the Tubercula 

 Q,uadrigemina, or the Medulla Oblongata, convulsions uniformly occur. This 

 result perfectly accords with what has been observed in Man ; for it has been 

 frequently remarked, when it has been necessary to separate protruded por- 

 tions of the Brain from the healthy part, that it has given rise to no sensation, 

 even in cases in which the mind has been perfectly clear at the time. The 

 effect of pressure upon the Brain is well known to be the suspension of all its 

 operations : this has been substantiated by experiments upon animals, and 

 also by similar experiments on persons who have had a portion of th *cranium 

 removed, so as to expose the membranes of the Brain. The pressure of the 

 finger upon the membranes occasions a state of immediate unconsciousness, 

 resembling profound sleep, which ceases as soon as the pressure is withdrawn. 

 Such pressure will, of course, affect the whole Encephalon, and not the Cere- 

 brum alone. Experiment does not throw much light on the particular func- 

 tions of the Corpus Callosum and other Commissures; since they can scarcely 

 be divided without severe general injury. It would appear, however, that the 

 partial or entire absence of these parts, reducing the Cerebrum to the level of 

 that of the Marsupial quadruped, or of the Bird, is by no means an unfre- 

 quent cause of idiocy. 



287. The information afforded by Pathological phenomena is far from being 

 definite. Many instances are on record, in which extensive disease has oc- 

 curred in one Hemisphere, so as almost entirely to destroy it, without either 

 any obvious injury to the mental powers, or any interruption of the influence of 

 the mind upon the body. But there is no case on record, of severe lesion of 

 both hemispheres, in which morbid phenomena were not evident during life. 



, It is true that, in Chronic Hydrocephalus, a very remarkable alteration in the 

 condition of the Brain sometimes presents itself, which might a priori have 

 been supposed destructive to its power of activity ; the ventricles being so 

 enormously distended with fluid, that the cerebral matter has seemed like a 

 thin lamina, spread over the interior of the enlarged cranium. But there is 

 no proof that absolute destruction of any part was thus occasioned; and it 

 would seem that the very gradual nature of the change gives to the structure 

 time for accommodating itself to it. This, in fact, is to be noticed in all dis- 

 eases of the Encephalon. A sudden lesion, so trifling as to escape observation, 

 unless this be very carfully 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 neighbourhood of the Corpora Striata; whilst, if it follow disorder of the 

 Brain of long standing, a much greater amount of lesion will usually present 



