NERVES OF THE SPINAL AXIS. 617 



sense of Taste. The muscles put in action by this division, are solely those 

 concerned in the masticatory movements. The Chorda Tympa.nl, though 

 essentially destined to excite the submaxillary gland to action, either directly 

 or indirectly, contains motor nerves, distributed to the muscles of the Tongue. 1 

 The 5th pair is connected, in different parts of its course, with a number of 

 small ganglia belonging to the Sympathetic system. One of the most interest- 

 ing of these ganglia is the Ophthalmic or Ciliary (Fig. 226, 29), which is the 

 centre whence the eyeball derives its supply of nerves, sensory, motor, and 

 sympathetic. This ganglion derives its sensory fibres by its "long root" 

 from the nasal branch of the Ophthalmic division of the 5th pair; its motor 

 fibres, by the " short root" from the 3d pair ; whilst by another small root, it 

 is connected with the cavernous plexus of the Sympathetic system, 2 and is 

 thus brought into relation with the Spinal axis; for, according to Budge, 3 

 these fibres of origin for the Sympathetic nerve arise from two centres : first, 

 from the Spinal Cord between the 6th cervical and the 2d dorsal vertebra 

 (a part which he terms the Centrum Cilio-spinale Inferius), the fibres from 

 which pass upward in the great cord of the Sympathetic ; and secondly, from 

 another centre situated in the Medulla Oblongata, in immediate proximity 

 to the origin of the Hypoglossal nerve, the fibres from this source passing 

 into the superior cervical ganglion. Valentin maintains that some of the 

 fibres of the Inferior Cilio-spinal ganglion ascend in the trunk of the 

 Pneumogastric. 4 



491. The Third, Fourth, and Si.rth pairs, together make up the apparatus 

 of motor nerves, by which the muscles of the Orbit are called into action. The 

 3d pair supplies the levator palpebrse, the superior, inferior, and internal 

 recti ; the circular fibres of the Iris and the Ciliary Muscle, or Tensor 



1 See Vnlpian, Gazette Hebdomadaire, 1873, No. 3. 



2 The functions of this ganglion have been made the subject of particular investi- 

 gation by Dr. C. Radclyffe Hall (Edinb. Med. and Surg. Journal, 1846-48), whose 

 most important results are as follows : 



1. The size of the c-iliary ganglion is always in direct proportion to the activity of 

 the iris, which in turn always bears a direct relation to the strength and acuteness 

 of vision, and to the nocturnal habits of the animal, and implies a proportionate 

 development of the internal vascular apparatus of the eye. 



2. The ganglion is always more intimately connected with the 3d pair than with 

 any other ; the size of the short root being always in direct relation to that of the 

 ganglion, and the ganglion being sometimes a mere swelling on the trunk of the 

 nerve. 



3. The fibres derived from the 5th pair do not terminate in the ganglion, but pass 

 onwards through it to the ciliary plexus. 



4. In the Rabbit, the iris receives fibres from the 6th pair which do not pass 

 through the ganglion ; and it is through this that the contraction of the pupil is 

 produced in that animal by irritation of the 5th pair, which will not produce any 

 effect upon the pupil of the Dog, Cat, or Pigeon, so long as it does not affect the 

 brain to the extent of producing vertigo, nor affect the visual sense in any other way. 



5. Irritation of the 5th nerve does not in any animal affect the action of the iris, 

 offer the division of the cerebral connections of all the other ocular nerves [this is 

 denied by Budge], so that its influence over the movements of the iris must be re- 

 flected through the encephalic centres, not through the ophthalmic ganglion. 



6. The function of the ganglionic centre itself, as a part of the Sympathetic system, 

 seems to be to bring the "organic actions " of the eyeball, especially its supply of 

 blood, into harmony with its functional activity; this harmony being produced by 

 the passage of the cerebro-spinal nerves through the ganglion, which excites the 

 synergetic action of its own vesicles and nerve-fibres. Irritation of the 3d pair of 

 nerves produces contraction of the pupil ; irritation of the cervical portion of the 

 Sympathetic, dilatation. On the other hand, paralysis of the 3d nerve is followed by 

 dilatation; paralysis of the cervical sympathetic (as by section), by contraction of the 

 pupil. 



3 Physiologic, 1862, p. 767. 4 See Schiff, Physiologic, p. 376. 



40 



