Page:Popular Science Monthly Volume 14.djvu/499

Rh making such an assertion, since his science takes no account of the base or internal parts of the brain—situations, forsooth, in which anatomy and the newer phrenology demonstrate the existence of very important sensory and other organs. The question of the relatively immense

 —(From Bourgery.) C. under surface of the cerebrum; cb, the cerebellum; m.ob, the medulla oblongata. The nerves are numbered 1 to 12; 1, the olfactory nerve; 2, the optic; 3, 4, and 6, nerves which govern the muscles of the eyeball; 5, the trigeminal, which arises as shown by two roots; 7, the facial; 8, the auditory; 9, the glosso-pharyngeal; 10, the pneumogastric; 11, the spinal accessory; 12; the several roots of the hypo-glossal. The figure 6 is placed on the pons varolii; the crura cerebri are between the third and fourth nerves on either side. Just above are a, the corpora albicanta, and P, the pituitary body.

tracts of brain which lie without the utmost ken of phrenology, even on its own showing, is also illustrated by the observation that the bulging or hollowing of the skull at any point affords no criterion of the thickness of the gray matter of the brain, a layer which we have already seen to constitute the most important part of the brain-substance. This gray matter is seen to exist in tolerable uniformity over large tracts of brain-substance, and it is invariably in the hinder region of the brain that it attains its greatest complexity and development. The form of the skull is dependent on the amount and disposition of the white matter, and not on that of the gray; and the former, as we have seen, has but a minor influence or part in the mental constitution, since its function is merely that of conducting and not of originating thoughts and impressions. Since, then, phrenology lays so much stress on skull-conformation as a clew to brain-structure, it must