938 



THE NERVES. 



Fig. 458. 



the crico-pharyngeal and crico-thyroid muscles. This filament either arises directly 

 from the pneumogastric nerve, or— as is most frequently the case — from the 

 pharyngeal ramuscule ; this is the external laryngeal nerve of anthropoto mists 

 (Fig. 458, 8). The external laryngeal receives accessory branches from the 



superior cervical ganglion, the oesopha- 

 geal branch, and the pharyngeal nerve, 

 and is then distributed to the muscular 

 tunic of the oesophagus. It is to the 

 union of this branch with the oesopha- 

 geal branch of the pharyngeal nerve, 

 that we have given the name of superior 

 msophageal nerves} 



4. Communicating Filaments 

 with the Inferior Cervical Gang- 

 lion. — These do not always directly 

 enter this ganglion, for when the middle 

 cervical ganglion exists they pass to it. 

 They are not similarly disposed on both 

 sides. The filaments of the right pneu- 

 mogastric, two or three in number, are 

 extremely short, though voluminous. 

 The left pneumogastric usually only 

 furnishes a single, long, thin ramuscule, 

 which is detached in the region of the 

 neck near the point where the pneumo- 

 gastric commences to separate from the 

 cervical branch of the sympathetic, and 

 reaches the inferior cervical branch of 

 the sympathetic, and reaches the inferior 

 cervical ganglion by remaining along- 

 side the principal nerve. 



5. Inferior Laryngeal Nerve 

 (Figs. 458, 2; 480, 27, 28).— Also 

 named the recurrent, or tracheal re- 

 car rent, because of its disposition. It 

 begins in the thoracic cavity, and 

 ascends along the trachea to the larynx, 

 the intrinsic muscles of which it stimu- 

 lates, with the exception of the crico- 

 thyroid. 



The two recurrent nerves are not 

 quite symmetrical at their origin. That 

 of the right side is detached from the 

 pneumogastric below the axillary artery, 

 near the dorso-cervical artery. It is 

 immediately reflected forward in em- 

 bracing the origin of that vessel, 

 against the trachea, in the middle 



DISTRIBUTION OF THE NERVES IN THE LARYNX 

 OF THE HORSE. 



R, Base of the tongue ; b, epiglottis ; c, arytsenoid 

 muscles; d, section of the thyroid cartilage to 

 show the parts it covers; e, cricoid cartilage; 

 /, trachea ; g, oesophagus ; h, thyro-arytsenoid 

 muscle; i, lateral crico-arytaenoid muscle; 

 j, posterior crico-arytaenoid muscle ; k, arytae- 

 noid muscle. 1, Superior laryngeal nerve ; 

 2, inferior laryngeal ; 3, branches of the 

 superior laryngeal passing to the epiglottis 

 and tongue; 4, branches of the superior laryn- 

 geal passing to the oesophagus ; 5, very fine 

 multiple anastomoses between the two laryn- 

 geals ; 6, tracheal branches ; 7, branch to the 

 posterior crico-arytienoid muscle (a portion is 

 distributed, through the muscles, to the 

 subjacent mucous membrane); 8. branch to 

 the lateral crico-arytaenoid muscle; 9, branch 

 to the thyro-aiyttenoid muscle ; 10, branch 

 passing to the aryt;enoid muscle; 11, oesopha- 

 geal branch of the pharyngeal nerve (it some- 

 times comes from the external laryngeal). 

 (From Toussaint's work.) 



which it crosses inwards to be placed 



' Toussaint lias seen this branch leave the oesophagus to lie beside the recurrent ; but its 

 filaments always return to that tube us ascending twigs. 



