The normal brain which exceeds the common limits of volume is not, in an absolute sense, incompatible with life. We need only to call to mind certain men of genius who had the brains of a giant.
Accordingly a brain which exceeds the limits demands of the individual who possesses it that he shall live according to certain special rules of hygiene. Children and young people who are too intelligent, too good, in other words, children of the elite class demand a special treatment, just as much as any other class of beings that pass beyond the bounds of average normality. Parents and teachers ought to be enlightened in regard to these scientific principles; the growth of individuals who are exceptional in regard to their intelligence and their emotions, should be supervised as though it were something precious and fragile. Such individuals are destined to be more subject than others to infective maladies, which frequently prove fatal, developing symptoms of meningitis and cerebral affections. Consequently a hygienic life, psychic repose, an avoidance of emotional excitement, moderate physical exercise in farm or garden, a prolonged stay in the open country, might be the salvation of children of this type, who often are over-praised and over-stimulated by friends and relatives, and consequently subjected to continual excitement and surménage to a degree destructive to their health.
Extreme Individual Variations of the Volume of the Brain.—In regard to individual variations, the authorities give various figures, from which the following have been selected as most noteworthy for their accuracy of research:
NORMAL EXTREMES OF INDIVIDUAL VARIATIONS IN THE VOLUME OF THE BRAIN
| Authors | Age: from 20 to 60 years | From 60 to 90 | ||
|---|---|---|---|---|
| Maximum | Minimum | Maximum | Minimum | |
| Calori | 1,542 | 1,024 | 1,485 | 1,080 |
| Bischoff | 1,678 | 1,069 | 1,665 | 1,080 |
| Without distinction of age: | ||||
| Broca | Maximum 1,830 | Minimum 1,049 | ||
These figures refer to individuals belonging to European races.
Comparison with the Brains of Apes.—The brain of the great anthropoid apes (Chimpanzee, Orang-utan, Gorilla), whose total weight of body is comparable to that of man, weighs on an average 360 grams, and the greatest weight which it can attain is 420 gr.
Specific Gravity of the Human Brain.—In normal individuals, the average specific gravity is 1.03; in insane persons it is slightly higher: 1.04.
The Relation between the Weight of the Brain and the Cranial Capacity: Figures given by Lebon: