. Anatomy, descriptive and applied. Anatomy. THE FOURTH OR TROCHLEAR NERVE 977 this latter a short, thick branch, radix brevis ganglii ciliaris, is given off to the lower ])art of the ciliary or lenticular ganglion and forms its short or motor root (Figs. 735 and 738). All these branches enter the muscles on their ocular surface, except that to the Inferior oblique, which enters its posterior border. Applied Anatomy.—Paralysis of the oculomotor nerve may be the result of many causes: as cerel)ral disease; conditions causing pressure on the cavernous sinus; periostitis of the bone entering into
. Anatomy, descriptive and applied. Anatomy. THE FOURTH OR TROCHLEAR NERVE 977 this latter a short, thick branch, radix brevis ganglii ciliaris, is given off to the lower ])art of the ciliary or lenticular ganglion and forms its short or motor root (Figs. 735 and 738). All these branches enter the muscles on their ocular surface, except that to the Inferior oblique, which enters its posterior border. Applied Anatomy.—Paralysis of the oculomotor nerve may be the result of many causes: as cerel)ral disease; conditions causing pressure on the cavernous sinus; periostitis of the bone entering into the formation of the sphenoidal fissure; fracture of the orbit. It results, when complete, in (1) ptosis, or drooping of the upper eyelid, in consequence of the Levator palpebrae being paralyzed; (2) external strabismus, on account of the unopposed action of the External rectus muscle, which is not supplied by the oculomotor nerve, and is not therefore paralyzed; (.3) dilatation of the pupil, because the sphincter fibres of the iris are paralyzed; (4) loss of power of accommodation, as the Sphincter pupillje, the Ciliary muscle, and the Internal rectus are paralyzed; (5) slight prominence of the eyeball, owing to most of its muscles being ^^Ocutomotor Nerve Fig. 735.—Plan of the oculomotor nerve. Occasionally paralysis may affect only a part of the nerve; that is to say, there may be, for ex- ample, a dilated and fixed pupil, with ptosis, but no other signs. Irritation of the nerve causes spasm of one or other of the muscles supplied by it; thus, there may be internal strabismus from spasm of the Internal rectus; accommodation for near objects only from spasm of the Ciliary muscle, or contraction of the pupil (myosis), from irritation of the sphincter of the pupil. The oculomotor nerve is particularly liable to become involved in a syphilitic periarteritis where it passes between the superior cerebellar and posterior cerebral arteries; associated with locomotor a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
