1886.] On the Intraocular Muscles of Mammals. 



479 



of (a) the third, (3) the nasal branch of the ophthalmic, and (7) the 

 sympathetic. 



a. The nerve to the inferior oblique muscle from the third nerve 

 generally gives off the branch to the ophthalmic ganglion, and from 

 this are given off the short ciliary nerves proceeding to a plexus iu 

 the ciliary muscle. 



(3. The nasal nerve gives off generally about four long ciliary 

 branches, which surround the optic nerve, piercing the sclerotic and 

 going to the plexus before mentioned. 



The nasal also gives off farther forward the long branch to the 

 ophthalmic ganglion. 



7. The sympathetic or so-called mydriatic nerve of tbe eye receives 

 from the lower cervical and upper dorsal part of the spinal cord fibres 

 generally by the second dorsal nerve. From the second dorsal they 

 pass to the superior thoracic ganglion of the sympathetic and by the 

 annulus Vieussenii to the inferior cervical ganglion, then along the 

 cervical sympathetic to the superior cervical ganglion, and through the 

 carotid canal to the Gasserian ganglion. From here they pass by 

 the nasal branch of the ophthalmic through the long ciliary nerves to 

 the plexus before described. 



This plexus situated in the ciliary muscle, and containing ganglion 

 cells, receives fibres from all three nerves ; from the plexus are given 

 off branches to the iris and ciliary muscle. 



(3.) A. The arteries of the iris come from the ciliary branches of 

 the ophthalmic, and are arranged at the ciliary border as the circulus 

 arteriosus iridis major, and from this are given off radial branches 

 proceeding towards the sphincter, and forming the circulus arteriosus 

 minor, which gives branches to the sphincter. The veins accompany 

 the arteries. 



B. The arteries of the ciliary body come from the long and anterior 

 ciliary and form an anastomosis behind the circle for the iris. 



II. The physiological action of the intra-ocular muscles may also 

 be classified under the headings of (1) the muscular tissue, (2) the 

 nerves, and (3) the vessels. 



(1.) A. Pupil. — Direct stimulation of the sphincter pupiliaB gives rise 

 to myosis in the normal eye ; this also takes place in the bloodless 

 and the exsected eye, and therefore after section of the various nerves 

 and vessels. 



On the iris cut out of the eye faradaic stimulation near the 

 pupillary border gives rise to contraction of the pupil. 



(2.) A. The nerves supplying the iris are a, the third ; |S, the sym- 

 pathetic or mydriatic ; 7, the trigeminus. 



a. (1.) Stimulation of third nerve or short ciliary nerves is followed 

 by myosis. 



(2.) Section of third nerve or short ciliary nerves gives rise to 



