Manual of human physiology / by Leonard Hill.

  • Hill, Leonard, Sir, 1866-1952
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Manual of human physiology / by Leonard Hill. Source: Wellcome Collection.

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    which also forms part of the inner wall of the orbit. The ethmoid separates the nose from the cranial cavity; it is pierced by many small holes through which pass the olfactory nerves to the brain. The lower jawbone is very strong and of an arched shape, bearing the sockets of the lower teeth. It is united by a joint to the temporal bone. The rest of the bones of the skull are joined together by irregular edges which fit into one another. Fig. 24. Skull divided in half to show the cranial cavity in which the brain is lodged. A. Parietal bone. B. Frontal. C. Air-spaces in frontal bone. D, Ethmoid. E. Vomer. F. occipital. G. Margin of foramen magnum. H. Temporal bone. I. Hole through which auditory nervepasses to ear. K. Sphenoid (air-spaces). L. Upper jawbone. Some of the bones of the skull, like the upper jaw and frontal bones, are not solid, but have within, in order to lighten their weight, large spaces full of air. Thus a pro- jecting forehead may indicate a large brain, but it may equally well indicate a large air-space. The skull is of great strength, in order that it may afford protection from external violence to the brain, the eye, and the ear; at the same time, it furnishes a powerful mill for tearing and grinding food. The head, by revolving upon the top of the spine, enables the eyes to sweep the horizon.