

THE CRANIAL OR ENCEPHALIC A/7. I BE 739 



the prolongation of the line of insertion of the inferior spinal roots, by a 

 dozen converging filaments. These traverse the dura mater in two or 

 three bundles, which enter the condyloid foramen of the occipital bone, 

 \vlu TO they unite to form a single cord. The hypoglossal has also a 

 ganglionic nx>t which Toussaint constantly found in the Ass, Mule, Ox, 

 anil Dog, and which had been previously seen by Meyer and Vulpian. 

 The ganglion of the hypoglossal in the Horse is fusiform, and the size of 

 a small lentil (Fig. 338, 5'). It is sometimes absent. 



Distribution. The hypoglossal nerve thus constituted, immediately after 

 its departure from the condyloid foramen, communicates with the first 

 cervical pair by means of a transverse ramuscule ; it then passes between 

 the spinal accessory and pneumogastric nerves, descends on the external 

 face of the guttural pouch, where it is connected with the superior cervical 

 ganglion of the sympathetic by numerous filaments, which in great part form 

 the plexiform network called the " guttural plexus." The nerve afterwards 

 crosses to the outside of the external carotid artery, in proceeding forward 

 and downward on the side of the pharynx and larynx, receiving at that 

 point a slender ramuscule from the first cervical; it then passes within the 

 inferior extremity of the stylo-hyoid muscle and the glosso-facial artery, 

 which it crosses very obliquely, is prolonged between the mylo-hyoid and 

 hyo-glossus brevis muscles, sends numerous small filaments to the latter and 

 a ramuscule to the genio-hyoideus, and finally terminates in a series of 

 brunches analogous to those of the gustatory nerve, and which mix with 

 them. 



These branches are therefore reflected upwards, bending round the 

 posterior border of the hyo-glossus brevis, and pass into the interstice between 

 that muscle and the genio-glossus. They are distributed to all the muscles 

 of the tongue. 



The hypoglossals, being motor nerves, cause the contraction of tho 

 muscles of the tongue during the movements proper to mastication and the 

 production of the voice. Though they most frequently act together, yet 

 they may do so separately, as in the unilateral movements of the tongue. 



DIFFERENTIAL CHARACTERS IN TUB CKAXIAL NfcUVES OF OTHER THAN 6OLHKH 



ANIMALS. 



In the domesticated mammals, tin rranial nerves offer Die greatest analogies ; tin ir 

 rL'in is the same in all, and it is only in their distribution that we find some vanYty, 

 due to the difference in the form of tlie IK ad. C<niM-<jiii-ntly, in lliis comparative analysis 

 we shall not di.-.-..vi-r any fundamental dilli rential characters. 



lit MisANTs. There is no differ* nee to notr in the four firft pairt. 



Triijtuiintil ,i> rre. Dividi d into three hnmehes as in S..lip.ds. It lia< U>en stated 

 that in Uiiminants the o|ihth:ilniie 1 nun-in - are distributed t'> tin- majority of the muscles 

 of tin- eye; in tin- Slin /, \sv have <>i:l_' - :> Ihe /.'/// ! ,i-i,-nn*<il m-rv.- oil' i .n^ this relation-. 

 ship to" tho motor organs of tbat port. The anterior jmlfttine nerve is relatively 



Volum.' 



Fai-int nerve Towards the middle of its Bubparotidml course, this gives off a large 



i-iciilnr nerve : when it urri\< at ihe middle of tin- jtostcrior border of tM 



I. r mu-ele. it .;i\id- -. into two hninehi s. Tin- Inh / ir l-raifh passes obliquely ilown- 



w.ird-s ai.il forwards, towards the mental foramen, when- it terminate- 



it furiiinhea an auastoinotic branch to the tnitfrior. The latter m--*.- the middle 



i of tin- m i. i-t'-r, and IM -comes mixe<l with Uiemborbltft] raimi-eiilesof tin- lil'tli pair ; 



alxut tin- middle of its course it receives a fila:aent from tho sii|ertii-ial tcmjH.ral n. rs. . 



it alludi- to the autlitvry and iil<>tM-i>liiirijii<ieal nerr*, except to say that the 



latter <-ommunirates with the pneumogastric soon . U fn-m th.- foramen lue.-riim. 



l'n' n in- i<i*ti -ic tierce. This offers unni<-:< "ts and distrihnt 



In tin- <>s an 1 NA-.y/, tin- * ,<>////< roott arise from an irregularly elliptical surface 



the \\holi- of the n--|-il ato.-y Ir.iet. Tie V are fp'111 lift--- li I" twenty ill 



