Human physiology : designed for colleges and the higher classes in schools and for general reading . would seem at first view that the gray substance, the workingpart of the cerebrum, is much less in amount than the whiteportion, which serves only for transmission. But this is not eye is deceived, because the white substance is all togetherin one central mass, while the gray substance is spread out inan external layer. This is very plainly illustrated by Fig. the area, a, contained in the inner circle, strikes the eye asbeing larger than the area, 6, included between the two ci
Human physiology : designed for colleges and the higher classes in schools and for general reading . would seem at first view that the gray substance, the workingpart of the cerebrum, is much less in amount than the whiteportion, which serves only for transmission. But this is not eye is deceived, because the white substance is all togetherin one central mass, while the gray substance is spread out inan external layer. This is very plainly illustrated by Fig. the area, a, contained in the inner circle, strikes the eye asbeing larger than the area, 6, included between the two circles,and yet these areas are precisely equal. 504. Observe for a moment in this connection the concurrentevidence, by which we determine what the function of the graysubstance of the brain is. It comes from two sources. Thefirst is that which is furnished to us by the structure of the cere-brum. As stated in § 206 and § 232, the gray portion ismade up of cells, while the white portion is composed of tubuh. 334 HUMAN PHYSIOLOGY. Quantity of the gray substance. Phrenology considered. FIG. These tubuli are such as we find in the nerves, and in fact arecontinuous with them. We very properly infer, therefore, thatas the nerves serve only for transmission, the white part of thebrain does the same. Is has, therefore, nothing to do with thethinking, and yet this we know from other facts, (§477 and499,) is done in some part of the cerebrum. So we infernecessarily that it must be done in the gray substance. Andhere, to confirm the truth of this inference, comes in one othersource of evidence, viz., the comparison between different ani-mals in regard to the correspondence between the amount ofthe gray substance and the amount of intelligence. This I re-marked upon in § 502, and need not dwell upon it farther. 505. This dependence of the mental faculties upon the graysubstance, the outer part of the brain, seems to give some coun-tenance to the doctrine of phrenology. But there
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