960 



THE SERVE SYSTEM 



olfactoria of the anterior commissure, a bundle of fibres passing from side to side 

 to end in the tract, granular stratum, and glomerular layer of the bulb. Further 

 connections are established with the tuber cinereum, mid-brain, and even spinal 

 centres; one division has been named the olfactomesencephalic tract (Wallenberg). 



The cingulum or fornix periphericus is an arcuate association bundle, or 

 rather an arcuate series of short bundles which establishes the connections of the 

 rhinencephalon w r ith the adjacent cortical areas (p. 956). 



Weight of the Brain. The average weight of the brain in the adult male is 1400 

 grams (49.5 ounces avoirdupois); that of the female, 1250 grams (44 ounces 

 avoirdupois). Among 1500 brains of males the brain weights ranged from 960 

 grams to over 1900 grams; the great majority of this series ranged from 1250 

 grams to 1500 grams. The average weight in the newborn is 400 grams (14.1 

 ounces avoirdupois) in the male and 380 grams (13.4 ounces avoirdupois) in the 

 female. The weight is doubled at the end of the first, and trebled at the end of the 

 fourth or fifth year, the female brain growing less rapidly than the male brain. 

 Brain growth generally ceases in the eighteenth or twentieth year, earlier in the 

 female than the male. After the sixtieth year the brain loses weight, at first 

 slowly, but more rapidly in advanced senescence. Other factors, besides age and 

 sex, which influence brain weight are stature, body weight, cranial form, and race. 

 Persons of large stature average heavier brains than those of short stature in abso- 

 lute figures, but not relatively. Brachycephalic persons average heavier brains 

 than the dolichocephalic. A most profound influence upon brain weight appears 

 to be exerted by racial differences. Representatives of the white race have heavier 

 brains than those of the other races, although data are not sufficient to make a 

 positive statement. Thus, the few Eskimo brains that have been secured so far 

 are notable for their size and weight. The following table gives approximately 

 accurate averages based upon greater or less numbers of brain weights: 



The intellectual status is in some way reflected in the mass and weight of the 

 brain. The average brain weight of 100 men eminent in the professions, arts, 

 and sciences, with an average age of sixty-two years, was 1470 grams (nearly 

 52 ounces avoirdupois), exceeding the average weight of the ordinary population 

 of about the same age by more than 100 grams (nearly 4 ounces avoirdupois). 

 A further analysis shows that the brains of men devoted to the higher intellectual 

 occupations, such as the mathematical sciences, involving the most complex 

 mechanisms of the mind, those of men who have devised original lines of research, 

 and those of forceful character are among the heaviest of all. 



The brains of microcephalic idiots are far under the minimal size necessary 



