THE ANATOMY OF BIRDS. — NEUROLOGY. 177 



ciivity between centres of orbito-sphenciid and alisplienoid, close to or in common with its 

 fellow. This nerve forms the retina of the eye. 3, 4, 6, the ocuU-motor, pathetic, ahducent, 

 collectively the motor nerves of the eye, supplying the muscles moving the eye-ball; 3, to all 

 these muscles excepting superior oblique and external rectus; origin from crura cerebri, base of 

 mesencephalon ; 4, to the superior oblique, origin behind optic lobes, uppier surface of meten- 

 cephalon ; 6, to external rectus (also to muscles of the third eyelid in birds) ; origin between 

 met- and myel-encephalon, base of brain ; 3, 4, 6, exits from cranial into orbital cavity by 

 several small, not constant, foramina near optic fi)ramen ; or by this foramen sometimes aU the 

 nerves which enter the orbit pass out of brain cavity through one great hole. 5, great trifacial 

 or trigeminal, sensori-motor ; feeling skin of head, moving muscles of jaws ; origin (double) 

 from myelencephalon ; leaves brain from sides of metencephalon ; sensory root has gasserian 

 ganglion; motor root simple. This nerve has three divisions, whence its name: 5a, ophthalmic 

 division, the most distinct ; exit from cranial into orbital cavity by separate foramen above 

 and to outer side of optic foramen ; grooves orbital wall in passing ; ciliary ganglion ; distri- 

 bution mainly to lacrymal and nasal jiarts ; traceable to end of upper mandible ; 56, superio-r 

 maxiUary : exit by foramen ovale, in alisphenoid or between that and prootic centre ; distribu- 

 tion to side of upper jaw ; meckelian ganglion ; 5c, inferior maxillary, derived chieily from 

 motor root; exit same as 56; distribution to lower jaw (muscles, substance of bone, integu- 

 ment); no special soise (gustatory) function; no otic ganglion. 7, facial or portio dura, 

 motor ; origin fi-om myelencephalon ; enters periotic bone, escapes from ear behind quadrate 

 bone, by what corresponds to stylo-mastoid foramen of mammals ; communicates with 5c by 

 chorda tympani nerve, with 9, 10, 13, and sympathetic system ; distribution to skin-muscles 

 and others of lower jaw and tongue, etc. 8, auditory or portio mollis, nerve of special sense 

 (hearing 1 ; origin with 7; no exit from skull; enters meatus auditorius interaus of periotic 

 bone; forms auditory apparatus in labyrinth of ear. 9, glosao-pharyngeal, mixed nerve, sensori- 

 motor and gustatory (taste) ; origin myelencephalon ; exit by foramen in exoccipital bone, 

 behind basitemporal, near lower border of tympanic recess ; distriliution to muscles and mem- 

 branes of gullet, throat, tongue, etc. 10, pneitmogastric, sensori-motor ; origin and exit next 

 to 9; distribution to windpipe, lungs, gullet, stomach, heart, etc. ; has recun-ent syringeal to 

 vocal organs. 11, spinal accessory, sensori-motor ;' origin upper jiart of spinal chord ; exit with 

 9, 10 ; distribution to these nerves and to muscles of neck. 9, 10,11, are intimately connected 

 with one another, and with other nerves, esjiecially 10 with sympathetic. The several f(jra- 

 niina in a bird's skuU which may be seen in the place indicated at 8, ligs. 69, 70, are for the 

 divisions of tliis composite vagus or " wandering" nerve of respiration, crrculaticju, digestion, 

 etc. ; they represent morphologically a foramen lacerum posterius, between exoccipital and 

 opisthotic centres. 13, hy2]oglos.ial, motor nerve of the tongue ; origin from myelencephalon ; 

 exit by anterior condyloid foramen in front of the occipital condyle. Thus the plan of the 

 cranial nerves of birds is nearly coincident with that of mammals. 



The Spinal Nerves, in pairs, correspond in a general way to the vertebra, between 

 which they pass out by intervertebral foramina , to supply the body at large. They are sensori- 

 motor; arise from the spinal chord by anterior motor and posterior sensory (ganglionatedl roots 

 which unite before lea\ing the spinal canal ; in the sacral region the main branches leave by 

 separate foramina. They form plexuses or interlacements. The principal of these is the 

 brachial plexus: constituted by several lower cervical nerves, and one or two usually counted 

 as dorsal, which combine to form a single chord, whence the nerves of the wing are derived. 

 Similar network of three to five true sacral nerves furnishes the nerves of the leg. 



The Sympathetic System consists of a pair of nervous chords miming lengthwise below 

 the bodies of the vertebrae, one on each side in the trunk, and in correspondingrelations with 



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