ANATOMY AND PHYSIOLOGY OF THE BRAIN 367 



tongue, jaw muscles). Junction of subfrontal fissure 

 with the precentral fissure. 



Auditory Perceptive Centre (word deafness, also the 

 lalognostic or word understanding centre). Marginal 

 fissure and adjacent parts of super- and meditemporal 

 fissure. 



Visual l\<'cc))lic<' Centre (word blindness). Angular 

 fissure. 



/'Jwmm' "Writing" Centre. Medif rental fissure, 

 in front of motor area for the upper limb (this has not 

 been definitely proved or accepted). 



Language Arrangement Centre. Island of Reil or 

 insular association area serving to connect the various 

 receptive sense areas relating to the* understanding 

 of the written and spoken word with the somesthetic 

 sensormotor emissary centre related to articulate 

 speech and writing. 



Association Areas. Under this heading are included 

 the frontal association area concerned, so far as is 

 known, with the powers of thought in the abstract, 

 creative, constructive, philosophic, the seat of the will, 

 memory. The parieto-occipito-temporal area is con- 

 cerned with the pow r ers of conception of the concrete, 

 for the comprehension of analogies, comparing, gen- 

 eralizing, and systematizing things heard, observed, 

 and felt (Gray). 



Sleep. Different theories have been proposed to 

 account for the causes of sleep, none of which has 

 been wholly satisfactory. 



The most generally accepted theory is based on the 

 decline in the irritability of the nerve cells of the brain 

 and associated sense organs, and the development of 

 fatigue conditions, the result of prolonged activity 

 (Brubaker). 1 



The Peripheral Nerve System. The peripheral 

 nerve system includes those nerve trunks which 



1 See chapter on arteries and veins for blood-supply of brain and 

 its membranes. 



