Page:Popular Science Monthly Volume 14.djvu/497

Rh Chalmers 53 ounces. As instances of high brain-weights, without corresponding intellectual endowment, may be mentioned four brains weighed by Peacock, the weights of which varied from 67·5 to 61 ounces. Several insane persons have had brains of 64 ounces, 63 ounces, 61 ounces, and 60 ounces, as related by Bucknill, Thurnam, and others. With respect to the brain-weights of the fair sex, anatomical authority asserts that in women with brains weighing 55·25 ounces and 50 ounces, no marked intellectual features were noted. Below 30 ounces, the human brain becomes idiotic in character, so that there appears to exist a minimum weight, below which rational mental action is unknown. The anatomist's conclusions regarding brain capacity and mental endowments are therefore plain. He maintains that the size and weight of the organ do not of themselves afford any reliable grounds for an estimate of the mental endowments, while his researches also prove that a large brain and high intellectual powers are not necessarily or invariably associated together.

The foregoing details will be found to assist us in our criticism of the pretensions of the old phrenology as a basis for estimating "the mind's construction" and the mental habits of man. Primarily, let us inquire if development—that great criterion of the nature of living structure—lends any countenance to the idea that the brain is a collection of organs such as the phrenologist asserts it to be. The brain of man, like that of all other backboned animals, appears to begin its history in a certain delicate streak or furrow which is developed on the surface of the matter of the germ. Within this furrow the brain and spinal cord are at first represented by an elongated strip of nervous matter, which strip, as the furrow closes to form a tube, also becomes tubular, and incloses within it, as the hollow of the tube, the little canal which persists in the center of the spinal cord. The front part of this nervous tube, which soon exhibits a division into gray and white matter, now begins to expand so as to form three swellings named vesicles. From these vesicles the brain and its parts are formed. The foremost swelling soon produces the parts known as the optic lobes, and also the structures which are destined to form the hemispheres or halves of the brain itself. The middle swelling contributes to the formation of certain important structures of the brain; and finally the cerebellum or lesser brain, along with the upper part of the spinal cord and other structures, appear as the result of the full development of the hinder or third swelling. Nor must we neglect to note that at first the human brain is completely smooth and destitute of convolutions, and only acquires its convoluted appearance toward the completion of development.

It is now an appropriate duty to inquire if the history of the brain's growth affords any countenance or support to the phrenological division of the organ into some thirty-five different organs and seats of faculties. The query is further a perfectly legitimate one. The