SUPERIOR AND INFERIOR LARYNGEAL NERVES. 609 



muscle with motor fibres, and sensory fibres to the lower lateral portion of the 

 laryngeal mucous membrane. (2) The internal branch gives off sensory branches 

 only to the glosso-epiglottidean fold, and the adjoining lateral region of the root of 

 the tongue, the aryepiglottidean fold, and to the whole anterior part of the larynx, 

 except the part supplied by the external branch {Longet). Stimulation of any of 

 these sensory fibres causes coughing reflexly. Coughing is produced by stimula- 

 tion of the boundaries of the glottis respiratoria, but not of the vocal cords, and 

 by stimulation of the sensory branches of the vagus to the tracheal mucous mem- 

 brane, especially at the bifurcation, and also from the bronchial mucous membrane 

 (Kohts). Coughing is also caused by stimulation of the auricular branch of the 

 vagus, especially in the deep part of the external auditory meatus, of the pulmonary 

 tissue, especially when altered pathologically ; in pathological conditions (inflamma- 

 tion) of the pleura (? certain changes in the stomach [stomach-cough]), of the liver 

 and spleen (Naunyn). The coughing centre is said to lie on each side of the 

 raphe, in the neighbourhood of the ala cinerea {Kohts). Cases of violent coughing 

 may, owing to stimulation of the pharynx, be accompanied by vomiting as an asso- 

 ciated movement ( 120). 



In many individuals, coughing can be excited by stimulation of distant sensory nerves ( 120, 1 ), 

 evg., from the outer ear (auricular nerve), nasal mucous membrane, liver, spleeu, stomach, 

 intestine, uterus, mammae, ovaries, and even from certain cutaneous areas {Ebstein). It is un- 

 certain if these conditions act directly upon the coughing centre, or first of all affect the vascu- 

 larisation and secretion of the respiratory organs, which in their turn affect the coughing centre. 



The cough (dog, cat) caused by stimulation of the trachea and bronchi occurs at once, and 

 lasts as long as the stimulus lasts ; in stimulation of the larynx, the first effect is inhibition 

 of the respiration accompanied by movements of deglutition, while the cough occurs after the 

 cessation of the stimulation {Kandarazky). 



The superior laryngeal contains afferent fibres which, when stimulated, cause arrest of the 

 respiration and closure of the rima glottidis {Rosenthal) (see Respiratory centre, 368). Lastly, 

 fibres which are efferent and serve to excite the vaso-motor centre, and are in fact " pressor 

 fibres" (see Vaso-motor centre, 371, II.). 



(b) The inferior laryngeal or recurrent bends on the left side around 

 the arch of the aorta, and on the right around the subclavian, and ascends in the 

 groove between the trachea and oesophagus, giving motor fibres to these organs, 

 and the lower constrictors of the pharynx, and passes to the laryux, to supply 

 motor fibres to all its muscles, except the cricothyroid. It also has an inhibitory 

 action upon the respiratory centre (see 368). 



A connecting branch runs from the superior laryngeal to the inferior (the anastomosis of 

 Galen), which occasionally gives off sensory branches to the upper half of the trachea (sometimes 

 to the larynx ?) ; perhaps also to the oesophagus {Longet), and sensory fibres (?) for the muscles 

 of the larynx supplied by the recurrent laryngeal. According to Francois Franck, sensory fibres 

 pass by this anastomosis from the recurrent into the superior laryngeal. According to Waller 

 and Burckhard, the motor fibres of both laryngeal nerves are all derived from the accessorius ; 

 while Chauveau maintains that the cricothyroid is an exception. 



Stimulation of the superior laryngeal is painful, and causes contraction of 



2, pharyngeal branches of vagus ; 6, pharyngeal branch of the glossopharyngeal ; 3, 

 superior laryngeal, with its anastomoses,/, with the sympathetic and its division, 4, into 

 its internal, v, and external branches, e ; 5, inferior or recurrent laryngeal ; au., auricular 

 branch of vagus. Cardiac nerves : g, cardiac branches from the vagus and superior lary n - 

 geal ; i, h, the three cardiac branches from the upper, g, middle, x, and lower, y, cervical 

 ganglion of the sympathetic ; k, ring of Vieusses ; I, cardiac branch from the recurrent 

 laryngeal ; L, lung with the anterior and posterior pulmonary plexuses ; r, oesophageal 

 plexus ; 00, gastric branches, and near them the hepatic branches, n ; m, cceliac plexus ; 

 k, splanchnic entering former ; 11, accessory nerve sending its inner branch into- the 

 gangliform plexus of the vagus its outer branch, ac, supplies the sternomastoid, St and 

 ac v and the trapezius, Cc ; 0, external auditory meatus ; Oh, hyoid bone ; K, thyroid 

 cartilage ; T, trachea ; H, heart ; P, pulmonary artery ; A A, aorta ; c, right carotid ; 

 c v left carotid ; s and s v right and left subclavian artery ; Z Z, diaphragm ; N, kidney ; Nn, 

 suprarenal capsule ; M, stomach ; m, spleen ; L L, lung and liver. II. Scheme of the 

 course of the depressor and accelerans in the cat. 



2Q 



