THE ANTHROPOLOGY OF THE BRAIX. 597 



III tlic brief space at my disposal 1 can bnt iiientioii two oftlic j;rcut 

 l)liysioloiii('al processes (•oiinect<Ml witli tlie brain. Proba])ly two of the 

 most eonspiciious activities of a human bein<;' are tliose of intellection 

 and locomotion; and, in consonance with this fact, we find the two por- 

 tions of the brain [(residing:: over these functions, the most conspicuous 

 and bulky sej;ments of it. The cerebrum is the physical basis of intel- 

 leetual processes and the c(M'ebellum of locomotion, in that the latter 

 is the great coordinating (*enter of the brain. 



Whether we extend our studies along the lines of phylogeny or 

 ontogeny, we will ol)serve that the rule is very general, almost uni\-er- 

 sal, that those animals having the largest cerebra ])ossess the gi'eatest 

 degree of intelligence, and those with the largest cerebella are capable 

 of the most varie<l and complii'ated motions. 



From an ethnological standpoint the size and weight of the human 

 brain are facts of great interest and importance. 



The size and weight of the brain are capable of Ix'ing estimated by 

 two methods, viz, the direct and indirect. The direct method is to 

 weigh the brain when it is accessible. The indirect is to ascertain the 

 cubical capacity of the cranium, and tluMi deduce the weighty of the 

 brain that once oc(;upied it. This latter method is ]>articularly ajtpli- 

 cable iu the study of the brains of ancient i)eoples, the skulls of which 

 have been preserved to this time. The a\'erage weight of the human 

 male adult brain is 1,390 grams. That of the female is 1,250 grams. 



The average cranial capacity of any race can only be determined by 

 careful examinati(m of a huge number of skulls classitied according to 

 sex; for sex exercises a most potent intiu<mce over cranial cai)acity, 

 often exceeding the difference of race. 



The following are some of the principal modifying conditions which 

 influence cranial capacity and thence biain weight, viz, age, weight of 

 body, stature, sex, race, vigor of intellect, and education. 



The earlier anatomists believed that the human brain attained its 

 maxinuim development at 7 years of age. We now know that this is 

 incorrect; yet from extensive researches it has been found that the 

 male brain does actually reach live-sixths of its ultimate weight by 

 the* end of the scNcnth year, and in the female ten-elcxcnths its ulti- 

 mate weight at tht^ cud of the same jH'iiod. 



The a\erage weight of the brain nndergoes a [)rogi'cssive increase up 

 to a ]>oint between tlu^ twentieth and fortieth years. Tiie gi-eatest ave- 

 rage weight fdi- the male bi'am is reached at from '.'A) to 10 years. 

 Women icach tlie lull average l)rain weight fiom tin- twentieth to the 

 thirtieth yeai'. 



There is a slight diminution in weight from 10 to 50 years of age, 

 and a still greater <liminution from 50 to <»0 years. The rate of 

 decrease is much greater after (JO years. In tlie eightieth year the 

 brain weight has <lecreased by from 80 to 00 grams. "'In the aged, 

 brain weight and intelligence doAtvesbi^e pari passu " (Thiirnam). 



