OPHTHALMIC GANGLION. One of the four ganglia connected with the branches of the fifth cranial nerve, and thought to be a part of the great sympathetic nerve. It is about the size of a pin's head, and situated at the back part of the orbit, between the optic nerve and the external rictus muscle. It lies in a quantity of loose fat which makes its dissection somewhat It has three branches of communication (motor, sensory, and sympathetic), which enter its pos terior border. The long branch (sensory) is de rived from the nasal branch of the ophthalmic nerve (first division of the fifth nerve). The second branch or root (motor) is derived from a branch of the third nerve supplying the inferior oblique muscle of the eyeball. The third branch. or root, is a slender filament from the cavernous plexus of the sympathetic. According to Tiede mann this ganglion receives a filament of com munieation from Meekel's ganglion (q.v.). Its branches of distribution are the short ciliary nerves. These are 10 or 12 delicate filaments arising from the fore part of the ganglion in two bundles. They run forward with the ciliary arteries, pierce the sclerotic coat at the back part of the globe, pass forward in delicate grooves on its inner surface, and are distributed to the ciliary muscle and the iris. It is therefore seen that the ophthalmic ganglion is one of the most important nerve centres in the whole body, al though no larger than a pin's head. The ciliary
muscle is the muscle of accommodation of the eye, causing variation in the form of the aqueous humor and the crystalline lens so as to accom modate the focal length of the eye to the dis tance of objects. Its supply of nerve force to the muscular fibres of the iris is also intimately connected with the focal length of the eye-appara tus.
The other three of the four ganglia above re ferred to are Meckel's (already described), the otic, and the submaxillary.
The otic (Arnold's) ganglion is a small, flat tened oval body reddish-gray in color, situated immediately below the foramen ()vale (through which the inferior maxillary nerve escapes from the cranial cavity). It is connected with the inferior maxillary, facial, and glossopharyngeal nerves, and with the sympathetic system, sending branches principally to the various parts of the tympanic cavity (middle ear), to which it serves much the same purpose that the ophthalmic ganglion does to the eye.
The submaxillary ganglion is a small fusiform body, situated above the submaxillary gland. It receives branches from the lingual, facial, and sympathetic nerves, and is distributed by five or six filaments to the mucous membrane of the mouth and the submaxillary gland, and indirect ly, it is thought, to the sublingual gland.