972 THE NERVOUS SYSTEM 



O/) The anterior auricular branches, usually two in number, are distributed to 

 the skin of the tragus and the upper and outer part of the pinna. 



(e) The superficial temporal branches supply the integument of the greater 

 part of the temuoral region, and anastomose with the temporal branch of the seventh 

 nerve. 



THE GANGLIA CONNECTED WITH THE BRANCHES OF THE TRIGEMINUS 



In addition to the semilunar (Gasserian) ganglion, which represents the ganglion of 

 the dorsal root of a nerve of spinal type, four other ganglia are connected with the 

 branches of the trigeminus. They are the ciliary, the spheno-palatine or Meckel's 

 ganglion, the otic, and the submaxillary. All these ganglia correspond both struc- 

 turally and developmentally with the sympathetic ganglia, and they are to be looked 

 upon as such. They are vagrant ganglia which separated from the embryonic 

 semilunar (Gasserian) ganglion at an early period of development and have become 

 associated with the branches of the fifth nerve, receiving fibres which pass through 

 them and constitute the so-called sensory roots of the ganglia. Each ganglion also 

 receives a motor root from a cranial nerve, most of the fibres of which root terminate 

 about its cells and each is connected with the sympathetic plexus on an adjacent 

 artery. 



THE CILIARY GANGLION 



The ciliary, lenticular, or ophthalmic ganglion, lies in the posterior part of the 

 orbital cavity, about 6 mm. in front of the superior orbital (sphenoidal) fissure, 

 to the outer side of the optic nerve, and between the optic nerve and the external 

 rectus muscle. It is a small, reddish, quadrangular body, compressed laterally, and 

 it measures about two millimetres from before backwards (fig. 701). 



Roots. (a) Its motor or short root enters its lower and posterior angle and is 

 derived from the branch of the lower division of the oculomotor nerve which sup- 

 plies the inferior oblique muscle. 



(6) The sensory or long root enters the upper and back part of the ganglion. 

 It is a branch of the naso-ciliary (nasal) nerve. 



(c) The sympathetic root consists of fibres derived from the cavernous plexus 

 . of the sympathetic; it passes to the ganglion with the long root. 



Branches. From six to eight short ciliary nerves emerge from the anterior 

 border of the ganglion; they divide as they pass forwards and eventually form about 

 twenty nerves which are arranged in an upper and a lower group, and the latter 

 group is joined by the long ciliary branches of the naso-ciliary (nasal) nerve (fig. 701). 

 When they reach the eyeball, the ciliary nerves pierce the sclerotic around the optic 

 nerve, and pass forward in grooves on the inner surface of the sclera. They are 

 distributed to the ciliary muscle, the iris, and the cornea. 



THE SPHENO-PALATINE OR MECKEL'S GANGLION 



This ganglion is associated with the maxillary nerve (fig. 702). It is a small 

 reddish-grey body of triangular form, which is flattened at the sides, and measures 

 about five millimetres from before backwards. It lies deeply in the pterygo-palatine 

 (spheno-maxillary) fossa at the outer side of the spheno-palatine foramen and in front 

 of the anterior end of the pterygoid (Vidian) canal. It is attached to the maxillary 

 nerve, from which it receives its sensory root, and it is connected with the Vidian 

 nerve, which furnishes it with motor and sympathetic filaments. 



Roots. (a) It is generally believed that the motor root is the great superficial 

 petrosal nerve which is incorporated in the Vidian nerve. It springs from the an- 

 terior angle of the geniculate ganglion and passes through the hiatus canalis facialis 

 (hiatus Fallopii) into the middle fossa of the cranium, where it runs forwards and in- 

 wards, in a groove on the upper surface of the petrous part of the temporal bone, to 

 the foramen lacerum, and in this part of its course it passes beneath the semi- 

 lunar (Gasserian) ganglion and the motor root of the fifth nerve. In the foramen 

 lacerum it joins with the great deep petrosal nerve to form the Vidian nerve (nerve 

 of the pterygoid canal), which passes forwards through the pterygoid (Vidian) canal 

 and terminates in Meckel's ganglion in the pterygo-palatine (spheno-maxillary) fossa. 

 The great superficial petrosal nerve contains sensory and possibly also motor fibres. 



