Archive image from page 757 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana01todd Year: 1836 Fig. 377. 742 CRANIUM. In infancy the rela- tive proportion of the cranium to the face is much greater than in adult life; and this causes the foramen magnum to appear to be situated much further forward, in the infe- rior region of the base, than it is when the face is more expanded. The lower part of the occiput is flattened, the superior is very projecting, and, altogether, the cranium has a character of rotundity which is speedily exchanged for the oval
Archive image from page 757 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana01todd Year: 1836 Fig. 377. 742 CRANIUM. In infancy the rela- tive proportion of the cranium to the face is much greater than in adult life; and this causes the foramen magnum to appear to be situated much further forward, in the infe- rior region of the base, than it is when the face is more expanded. The lower part of the occiput is flattened, the superior is very projecting, and, altogether, the cranium has a character of rotundity which is speedily exchanged for the oval form which prevails in the adolescent age. When the sutures have become conjoined, and the cranium is constituted a defensive in- vestment of the brain in virtue of its mechan- ism, the internal table (the tabula vitrea) is secreted in greater abundance, and the diploe between it and the outer table is rendered more manifest. The spongy tissue of the sphenoid bone is absorbed and the sinuses formed ; but it is not until a period nearly coeval with puberty, that those of the frontal bone are developed. It is not until the diploe is fully formed that we can demonstrate those venous canals with which that structure has been shown to abound by the researches of Chaussier, Dupuytren, and Breschet (figs. 187, 188, p. 436). Mechanical adaptation of the cranium.—It will now be noticed that the properties of the cranium, those on which its defensive qualities are founded, differ in the several periods of life; but that, nevertheless, there is in each as perfect an adaptation of it to these purposes as seems consistent with the schemes of Provi- dence in the creation of a finite being. The pressure which the brain has to sustain during the process of parturition, is directed solely to that part which is not essential to life; the condition of the bones of the calvaria ad- mits of the volume of the hemispheres being diminished at the time the foetus is ushered into the world. Not so
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