208 FUNCTIONS OF THE BRAIN. 



feet vascular net-work. This minute subdivision is 

 of use in preventing the blood from being impelled 

 with too great force against the delicate tissue of 

 the brain. 



A third covering, called the arachnoid membrane, 

 from its fineness resembling that of a spider's web, 

 is interposed bet ween the other two, and is frequently 

 the seat of disease. 



On examining the convolutions in different brains, 

 they are found to vary a good deal in size, depth, 

 and general appearance. In the various regions of 

 the same brain they are also different, but preserve 

 the same general aspect. Thus they are always 

 small and numerous in the anterior lobe, larger and 

 deeper in the middle, and still larger in the posterior 

 lobe. 



The brain receives an unusually large supply of 

 blood, in comparison with the rest of the body ; but 

 the nature of its circulation, although a very interest- 

 ing subject of study, being only indirectly con- 

 nected with our present purpose, cannot now be dis- 

 cussed. 



Most physiologists are agreed that the different 

 parts of the brain perform distinct functions, and that 

 these functions are the highest and most important 

 in the animal economy ; but there is great discrep- 

 ancy of opinion as to what the function of each part 

 is, and as to the best mode of removing the obscu- 

 rity in which the subject is involved. It would be 

 useless to examine here the merits of the respective 

 theories and modes of inquiry, as the attempt would 

 lead us too far from the practical aim of the work. 

 Suffice it to say, that all physiologists and philoso- 

 phers regard the brain as the organ of mind ; that 

 most of them consider it as an aggregate of parts, 

 each charged with a specific function ; and that a 

 large majority, with Gall and Cuvier at their head, 

 regard the anterior lobe as more immediately the 



