THE BRAIN 729 



the monkey, it induces a pricking of the opposite ear, with a rotation 

 of the head to the opposite side. Ablation effects are not so con- 

 clusive, as it is difficult to tell whether an animal, like a monkey, is 

 deaf or not. Clinical evidence points to the central part of the lobe as 

 the true receiving station the audito-sensory area and to the area 

 just behind this as the part concerned in the psychic processes the 

 appreciation of the s : gnificance of the sound heard. 



The receiving stations for taste and smell are probably present in 

 the anterior part of the temporal lobe, particularly in the deeper 

 aspects. Electrical stimulation of the hippocampal region causes 

 movement of the nostril and lip of the same side. The evidence of 

 the effects of ablation and of clinical observation are by no means: 

 conclusive. It has been suggested that sensations of hunger and 

 thirst are received in the cortex of the anterior part of the temporal 

 lobe in its outer part. 



The Association Areas. The cortex as a whole is to be regarded 

 as one great association centre concerned in the storing of sensations 

 as memories, and the association of present with past impressions, 

 resulting in the power of discrimination, inhibition of emotion, and 

 judgment. There is evidence that there is some localization of these 

 functions. It has already been pointed out that the external aspect 

 of the occipital lobe in man is concerned with the appreciation of the 

 significance of things seen. Further, in the angular gyrus of the brain, 

 on the left side in right-handed people, there is thought to be the 

 " visual word area," by means of which the meaning of written words 

 is appreciated. So, in regard to hearing, it has been pointed out that 

 the posterior part of the temporal lobe is probably concerned in the 

 appreciation of the meaning of the sound heard, and in this region is 

 also situated the auditory word centre, which enables the appreciation 

 of the word heard. 



These centres belong to one of the three great areas which have 

 been designated as association areas. These areas are the posterior 

 in the parieto-temporal region chiefly concerned in sensorial 

 function; the middle in the island of Reil; and the anterior in 

 the pref rental region. All these regions are intimately connected 

 by association fibres. The exact function of the island of Reil is 

 not known. In regard to the frontal region, it is suggested that this 

 is the centre concerned in voluntary attention, memory, and thought. 

 Dementia is associated with the disorder of this region, the degree 

 of permanency varying according to the degree of dissolution of the 

 area. If this region be not developed, then the subject is generally 

 permanently imbecile (amentia), temporarily insane, or liable to the 

 onset of insanity. In the frontal region the outer cell lamina 

 is particularly well marked. It is the last to develop, the first 

 to regress. 



Speech. The functions of the cerebral cortex are well illustrated in 

 the power of speech. To give an answer to a question directed ix> 

 him, a man must 



