456 



PHYSIOLOGY 



hearing and sight. It may therefore be spoken of as an intellectual centre. 

 Pure motor aphasia of course exists, but is always anarthria and is due to a 

 lesion in the lenticular zone, i.e. in the lenticular nucleus and its neighbour- 

 hood, in the anterior part and the genu of the internal capsule, and possibly 

 in the external capsule. 



Amenta Dementa 



(-0 



(5) 



FIG. 235. Types of lesions giving rise to deficient intellectual power. In amentia, 

 the deficiency is due to failure of development ; in dementia, to atrophy of 

 the cells (especially small pyramidal) previously present in the cortex. (MoTT.) 



It is important to make a distinction between loss of sanity and loss 

 of intellectual powers. The essential factor of sensory aphasia is the exist- 

 ence of intellectual impairment, though in his behaviour the patient may 

 appear perfectly normal. On the other hand, in insanity there may be 

 perfect retention of the intellectual processes, which depend on the proper 

 working of the lower association centres. The personality of the individual, 

 and therefore finally his behaviour, involves a further association on a higher 

 plane of these intellectual processes and therefore control in accordance with 

 the relation, past, present, or future, of the individual to his environment. 



