The cranial nerves

The facial or seventh nerve is purely motor. It is accompanied a short distance by a bundle usually called its sensory root or the intermediate nerve.

The fibers of the optic nerve are the central processes of the ganglion cells of the retina. Within the ocular bulb they converge to the optic papilla, where they are accumulated into a rounded bundle, the optic nerve.

The trigeminus is the largest of the cranial nerves with the exception of the optic. It is usually described as the fifth cranial nerve and as possessing both a sensory and a motor root.

The olfactory nerve-fibers are the central processes of the bipolar olfactory nerve cell-bodies situated in the olfactory region of the nasal mucous membrane. In man, the olfactory region comprises the epithelium upon the superior third of the nasal septum and that upon practically the whole of the superior nasal concha.

The fibers of each trochlear or fourth nerve (or patheticus) spring from the cells of a nucleus which lies in the grey substance of the floor of the cerebral aqueduct in hne with the oculo-motor nucleus, but in the region of the inferior quadri-geminale bodies.

Customarily, the cranial nerves are described as comprising twelve pairs and each is referred to by number.

The oculo-motor or third cranial nerve is a purely motor nerve. Each supplies seven muscles connected with the eye, two of which, the sphincter of the iris and cihary muscle, are within the ocular bulb.

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