THE CRANIAL NERVES. 



605 



2. An external branch, consisting chiefly of the accessory fibers from the 



spinal cord. 

 It is distributed to the sterno-cleido-mastoid and trapezius muscles. 



Cortical Connections. The nucleus of origin of the medullary branch 

 at least, is in relation with nerve-cells in 

 the lower third of the general cerebral 

 motor area, the axons of which descend 

 in the pyramidal tract. 



Properties. Faradization of the me- 

 dullary portion of the nerve near its 

 origin gives rise to contraction of the 

 muscles to which it is distributed. De- 

 struction of the medullary root is followed 

 by impairment of deglutition from a 

 paralysis of the muscles of the pharynx 

 and palate and a loss of the power of pro- 

 ducing vocal sounds on account of pa- 

 ralysis of the constrictor muscles of the 

 larynx. According to some authorities, 

 there is also an acceleration of the heart's 

 action from a loss of inhibitor influences. 



Stimulation of the external branch 

 gives rise to contraction of the sterno- 

 cleido-mastoid and trapezius muscles, 

 though division of the branch does not 

 give rise to complete paralysis, as they 

 are supplied with motor fibers also from 

 the cervical nerves. In consequence of 

 division of the external branch animals 

 experience extreme shortness of breath 



during exercise, from a Want Of COOrdma- Glosso-pharyngeal nerve. 3, 3 Pneumo- 



tion Of the muscles Of the fore-limbs and gastric. 4,4,4. Trunk of the spinal acces- 



tVi^ mncrlpQ nf rpcnirarirm sor y- 5- Sublmgual nerve. 6. Superior 



me muscles Ol respiration. ^ cervical ganglion. 7, 7. Anastomosis of 



Functions. The function Of the the first two cervical nerves. 8. Carotid 



fibers of the spinal accessory nerve is branch of the sympathetic. 9, 10, n 



. . x - ' i f 12,13. Branches of the glosso-pharvngeal. 



the transmission of nerve impulses from I4> Branches of the facial 16. Otic 



the Cells from which they take their ganglion. 17. Auricular branch of the 



origin to the muscles to which they are FZTh? a ^al \cce~tf"h g e" 

 distributed. They therefore excite to mogastric. 19. Anastomosis of the first 



action some Of the muscles Of deglutition; Pair of cervical nerves with the sublingual. 



the muscles which regulate the tension ^^^^^^^7. 



Of the VOCal bands during phonation and Pharyngeal plexus. 22. Superior laryn- 



the muscles which control the respiratory g eal ""T/ 2 3- External laryngeal nerve. 

 , . , , . j 24. Middle cervical ganglion. (Hirsch- 



movements associated with sustained or jdd ^ 



prolonged muscle efforts. The fibers 



may also convey nerve impulses which exert an inhibitor influence on the 



heart. 



