THE BRAIN AND ITS MEMBRANES. 789 



Weight of the Encephalon. The average weight of the brain in the adult male 

 is 4UJ oz., or a little more than 3 Ibs. avoirdupois; that of the female 44 oz. ; the 

 average difference between the two being from 5 to 6 oz. The prevailing weight 

 of the brain in the male ranges between 46 oz. and 53 oz., and in the female 

 between 41 oz. and 47 oz. In the male the maximum weight out of 278 cases A\as 

 65 oz., and the minimum weight 34 oz. The maximum weight of the adult female 

 brain, out of 191 cases, was -Itj oz., and the minimum weight 31 oz. According to 

 Luschka, the average weight of a man's brain is 1424 grammes (about 45 oz.), 

 of a woman's 1272 grammes (about 41 oz.), and, according to Krause, 1570 

 grammes (about 48| oz.) for the male, and 1350 (about 43 oz.) for the female. It 

 appears that the weight of the brain increases rapidly up to the seventh year, more 

 slowly to between sixteen and twenty, and still more slowly to between thirty and 

 forty, when it reaches its maximum. Beyond this period, as age advances and the 

 mental faculties decline, the brain diminishes slowly in weight, about an ounce 

 for each subsequent decennial period. These results apply alike to both sexes. 



The size of the brain was formerly said to bear a general relation to the intel- 

 lectual capacity of the individual. Cuvier's brain weighed rather more than 64 oz., 

 that of the late Dr. Abercrombie 63 oz., and that of Dupuytren 62J oz. On the 

 other hand, the brain of an idiot seldom weighs more than 23 oz. But these facts 

 are by no means conclusive, and it is well known that these weights have been 

 equalled by the brains of persons who never displayed any remarkable intellect. 

 Dr. Haldennan of Cincinnati has recorded the case of a mulatto, aged forty-five, 

 whose brain weighed 68| oz. ; he had been a slave, and was never regarded as 

 particularly intelligent ; he was illiterate, but is said to have been reserved, medi- 

 tative, and economical. Dr. Ensor, district medical officer at Port Elizabeth, 

 reports that the brain of Carey, the Irish informer, weighed 61 oz. M. Xikiforoff 

 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 necessarv 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. 



Cerebral Localization and Topography. Within the last few years physiological and 

 pathological research have 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. Ami this is especially true with regard to the convolutions on either side of the fis- 

 sure 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 woodcuts from Ferrier (Figs. 471, 472) have been introduced, and will serve to 

 indicate the position of these areas as far as they have been at present ascertained. 



The relation of the principal fissures and convolutions of the cerebrum to the outer surface 

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

 devised by which one may localize these parts from an examination of the external surface of 

 the head. 



These plans can only be regarded as approximately correct for several reasons : in the first 

 place, because the relations of the convolutions and sulci to the surface are found to be very 

 variable in different individuals ; secondly, because the surface area of the scalp is greater than 

 the surface area of the brain, so that lines drawn on the one cannot correspond exactly to sulci 

 or convolutions on the other ; and thirdly, because the sulci and convolutions in two individuals 

 are never precisely alike. Nevertheless, the principal fissures and convolutions can be mapped 



