THE BRAIN AND ITS MEMBRANES. 



705 



has published an article on the subject of the weight of brains in the Novosti. 

 According to him, the weight of the brain has no influence whatever on the 

 mental faculties. It ought to be remembered that the significance of the weight 

 of the brain should depend upon the proportion it bears to the dimensions of the 

 whole body and to the age of the individual. It is equally important to know 

 what was the cause of death, for long illness or old age exhausts the brain. To 

 define the real degree of development of the brain it is therefore necessary to 

 have a knowledge of the condition of the whole body, and, as this is usually 

 lacking, the mere record of weight possesses little significance. 



The human brain is heavier than that of all the lower animals, excepting the 

 elephant and whale. The brain of the former weighs from eight to ten pounds ; 

 and that of a whale, in a specimen seventy-five feet long, weighed rather more 

 than five pounds. 



FIG. 375. Drawing to illustrate cranio-cerebral topography. (Taken from a cast in the Museum of the Royal 

 College of Surgeons of England, prepared by Professor Cunningham.) 



Cerebral Localization and Topography. Physiological and pathological research have 

 now gone far to prove that the surface of the brain may be mapped out into series of definite 

 areas, each one of which is intimately connected with some well-defined function. And this is 

 especially true with regard to the convolutions on either side of the fissure of Rolando, which 

 are believed by most physiologists of the present day to be concerned in motion, those grouped 

 around the fissure being associated with movements of the extremities of the opposite side of 

 the body, and those around the lower end of the fissure being related to movements of the 

 mouth and tongue. 



This is not the place, nor can space be given, to describe these localities. But the two 

 accompanying cuts from Ferrier (Figs. 373, 374) have been introduced, and will serve to indi- 

 cate the position of the more important areas. 



The relation of the principal fissures and convolutions of the cerebrum to the outer sur- 

 face of the scalp has been the subject of much investigation, and many systems have been 

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