TABLE V
MAXIMUM BRAIN-WEIGHTS—ST. MARYLEBONE
| Age. | Male. | Female. | ||
| Oz. | Grms. | Oz. | Grms. | |
| 7-14 | 57.25 | 1622 | 52.00 | 1473 |
| 14-20 | 58.50 | 1658 | 52.00 | 1473 |
| 20-30 | 57.00 | 1615 | 55.25 | 1565 |
| 30-40 | 60.75 | 1721 | 53.00 | 1502 |
| 40-50 | 60.00 | 1700 | 52.50 | 1488 |
| 50-60 | 59.00 | 1672 | 52.50 | 1488 |
| 60-70 | 59.50 | 1686 | 54.00 | 1530 |
| 70-80 | 55.25 | 1565 | 49.50 | 1403 |
| 80 | 53.75 | 1523 | 48.00 | 1360 |
| All Ages. | ||||
| 7-80 | 60.75 | 1721 | 55.25 | 1565 |
The stature, or relative size of body, has already been referred to as an element in testing the comparative male and female weight of brain; and it is one which ought not to be overlooked in estimating the comparative size and weight of the brains of distinguished men. From my own recollections of Dr. Chalmers, who was of moderate stature, his head appeared proportionally large. The same was noticeable in the cases of Lord Jeffrey, Lord Macaulay, Sir James Y. Simpson, and very markedly so in that of De Quincey. The philosopher Kant was also of small stature; and Dr. Thurnam refers to the observation of Carus that he had a head not absolutely large, though, in proportion to the small and puny body of that eminent thinker, it was of remarkable size. Among the large-brained artizans of the Marylebone Infirmary, on the contrary, the probabilities are in favour of a majority of them being men of full muscular development and ample stature. Nevertheless, with every allowance for this, it still remains probable, if not demonstrable, that from the same humble and unnoted class, examples of megalocephaly could be selected little short in cerebral mass, and apparently in brain-weight, of the group of men whose large brains are recognised as the concomitants of exceptionally great mental capacity and intellectual vigour. Unless, therefore, we are contented to accept the poet’s dictum, “Their lot forbad,”[[175]] and assume that “chill penury repressed their noble rage, and froze the genial current of the soul,” it is manifest that other elements besides those of volume or weight are essential as cerebral indices of mental power. Dr. Thurnam, after noting examples that had come under his own notice of brain-weights above the medium—but which, as those of insane patients, may be assigned to other causes than healthy cerebral development,—adds: “The heaviest brain weighed by me (62 oz., or 1760 grms.) was that of an uneducated butcher, who was just able to read, and who died suddenly of epilepsy, combined with mania, after about a year’s illness. The head was large, but well-formed; the brain of normal consistence; the puncta vasculosa numerous.” In cases like this, of weighty brain with no corresponding manifestation of intellectual power, something else was wanting besides an ampler sphere. The mere position of a humble artizan or labourer will not suffice to mar the capacity to “make by force his merit known,” which pertains to the “divinely gifted man.”
Arkwright, Franklin, Watt, Stephenson, Farraday, Hugh Miller, and others of the like type of self-made men, are not rare. Among the large-brained artizans, scarcely one can have had a more limited sphere for the exercise of mental vigour than the poet Burns, the child of poverty and toil, who refers to his own early years as passed in “the unceasing moil of a galley-slave.” In his case the very means essential to a healthy physical development were stinted at the most critical period of life. His brother Gilbert says: “We lived sparingly. For several years butcher’s meat was a stranger to the house; while all exerted themselves to the utmost of their strength, and rather beyond it, in the labours of the farm. My brother, at the age of thirteen, assisted in thrashing the crop of corn, and at fifteen was the principal labourer on the farm.” Such premature toil and privations left their permanent stamp on his frame. “Externally, the consequences appeared in a stoop of the shoulders, which never left him; but internally, in the more serious form of mental depression, attended by a nervous disorder which affected the movements of the heart.” He had only exchanged the toil on his father’s farm for equally unremitting labour on his own, when the finest of his poems were written; nor would it be inconsistent with all the facts to assume that the privations of his early life diminished his capacity for continuous mental activity; as it undoubtedly impaired his physical constitution. But, while the possession of a brain much above the average in size might have seemed to account for his triumph over the depressing influences of his limited sphere, the fact that his brain appears to have been below the average size, points to some other requisite than mere cerebral mass as essential to intellectual vigour.
The brain is influenced in all its functions by the character and the amount of blood circulating through it, and promptly manifests the effects of any deleterious substance, such as alcohol or opium, introduced into its tissues. It depends, like other portions of the nervous system, on an adequate supply of nourishment. In both respects the brain of the Ayrshire poet was injuriously affected, in so far as we may infer from all the known circumstances of his life.
The human brain is large in proportion to the body in infancy and youth; and the opinions of leading anatomists and physiologists early in the present century favoured the idea that it attained its full size within a few years after birth. Professor Sœmmering assumed this to take place so early as the third year. Sir William Hamilton explicitly stated his conclusion thus: “In man the encephalon reaches its full size about seven years of age”; and Tiedemann assigns the eighth year as that in which it attains its greatest development. But the more accurate and extended observations since carried on rather tend to the conclusion that the brain not only goes on increasing in size and weight to a much later period of life; but that it is healthfully stimulated by habitual activity, and under exceptionally favouring circumstances it may increase in weight long after the body has attained its maximum.
The largest average brain-weights, as determined by observations on the brains of upwards of 2000 men and women in different countries of Europe, have indeed been found in those not above twenty years of age; and from a nearly equal number of English examples, Dr. Boyd determines the period of greatest average weight to be the interval between fourteen and twenty years of age; but this includes cases in which death has ensued from undue or premature brain development.
Other evidence leaves no room for doubt that cases are not rare of the growth, or increased density of the brain up to middle age; while the observations of Professor Welcker indicate this process extended to a later period of life. The average brain-weights, as given by Boyd, Peacock, and Broca, from healthy or sane cases, along with those of Welcker, include the weights of 47 male brains from ten to twenty years of age, giving an average of 49.6 oz., or 1405 grms.; and of 112 male brains from twenty to thirty years of age, giving an average of 48.9 oz., or 1384 grms.; and the results of a nearly equal number of female brains closely approximate. They embrace English, Scotch, German, and French, men and women. Dr. Welcker’s results indicate the period of maximum brain-weight to be between 30-40, as shown in the following table:—