66 THE CRANIAL NERVES. 



bone and the thyroid cartilage, where it perforates the thyro-hyoid membrane with 

 the laryngeal branch of the superior thyroid artery, and breaks up into numerous 

 diverging branches which supply the mucous membrane of the greater part of the 

 larynx. Some of these ascend in the ary-epi glottic fold to the base of the tongue and 

 the epiglottis ; while others pass downwards to the false vocal cord, and also to the 

 part of the pharyngeal mucous membrane covering the back of the larynx. One 

 long branch descends beneath the ala of the thyroid cartilage, and joins at the lower 

 part of the larynx a similar offset ascending from the recurrent laryngeal nerve. 



Varieties. The superior laryngeal nerre may pass on the outer side of the internal carotid 

 artery. The external laryngeal branch often arises separately from the main trunk. Offsets 

 of the external laryngeal nerve have been described by different anatomists as passing to the 

 pharyngeal plexus, to the thyroid body, to the sterno-hyoid, sterno-thyroid, and thyro-hyoid 

 muscles, to the lateral crico-arytenoid muscle, and to the mucous membrane of the true vocal 

 cord and lower part of the larynx. The internal laryngeal IrancJi has been seen piercing the 

 thyroid cartilage. 



A middle laryngeal nerve is described by S. Exner as a slender offset from the pharyn- 

 geal plexus (in the rabbit and dog directly from the pharyngeal branch of the vagus), which 

 is distributed to the crico-thyroid muscle, and to the mucous membrane of the lower part of the 

 larynx by means of twigs which perforate the crico-thyroid membrane. ( i; Die Innervation 

 des Kehlkopfes." Wiener Sitzungsber., 1884.) 



Inferior laryngeal nerve. The inferior or recurrent laryngeal nerve of the 

 right side arises at the root of the neck, and turns backwards below the subclavian 



Fig. 181. VlEW OF THE DISTRIBUTION AND CONNECTIONS OF THE PNEUMO-GASTRIC AND SYMPATHETIC 



NERVES ON THE RIGHT SIDE. (Hirschfekl and Leveille. ) 



a, lachrymal gland ; 6, sublingual gland ; c, submaxillary gland and facial artery ; d, thyroid body ; 

 c, trachea, below which is the right bronchus cut across ; /, resophagus ; g, stomach, divided near the 

 pylorus ; i. transverse colon ; r, the diaphragm. 



A, heart ; B, aorta, drawn forwards to show the cardiac plexus ; C, innominate artery ; D, subcla- 

 vian ; E, inferior thyroid ; F, a detached part of the external carotid, upon which runs a nervous plexus ; 

 G, internal carotid emerging from its canal superiorly ; H, descending thoracic aorta ; K, intercostal 

 vein ; L, pulmonary artery ; M, superior vena cava ; 0, intercostal artery. 



1, ciliary nerves ; 2, branch of third nerve to inferior oblique muscle ; 3, 3, 3, the three divisions of 

 the fifth nerve ; 4, ciliary ganglion ; 5, spheno-palatine ; 6, otic ; 7, submaxillary ; 8, sublingual ; 9, sixth 

 nerve ; 10, facial in its canal, uniting with the spheno-palatine and otic ganglia ; 11, glosso-pharyngeal ; 

 12, right pneumo-gastric ; 13, left pneumo-gastric spreading on the anterior surface of the stomach ; 14, 

 spinal accessory ; 15, hypoglossal ; 16, 16, nerves of cervical plexus ; 17, middle trunk of brachial plexus ; 

 18, intercostal nerve ; 19, lumbar nerve ; 21, superior cervical ganglion ; 22, tympanic nerve ; 23, 

 large superficial petrosal nerve ; 24, cavernous plexus ; 25, sympathetic root of ciliary ganglion ; 26, fila- 

 ment to pituitary body ; 27, union of sympathetic with upper cervical nerves ; 28, pneumo-gastric nerve ; 

 29, superior laryngeal nerve ; 30, pharyngeal plexus ; 31, cord of sympathetic ; 32, superior cardiac 

 nerve ; 33, middle cervical ganglion ; 34, twig connecting the ganglion with, 35, the recurrent ; 36, 

 middle cardiac nerve ; 37, cord of sympathetic ; 38, inferior cervical ganglion ; 39, the line from this 

 number crosses the nerves proceeding from the brachial plexus ; 40, sympathetic twigs surrounding the 

 axillary artery ; 41, branch of union with the first intercostal nerve ; the line from the letter e, pointing to 

 the trachea, crosses the superior, middle, and inferior cardiac nerves ; 42, cardiac plexus ; 43, 44, right 

 and left coronary plexuses ; 45, 46, thoracic portion of the sympathetic cord ; 47, great splanchnic 

 nerve ; 48, semilunar ganglion ; 49, lesser splanchnic ; 50, solar plexus ; 51, union with the pneumo- 

 gastric rerve ; 52, diaphragmatic plexus ; 53, gastric plexus ; 54, hepatic ; 55, splenic ; 56, superior 

 mesenteric ; 57, renal plexus ; 58, first lumbar sympathetic ganglion. 



artery ; the nerve of the left side arises in the upper part of the thorax, and is re- 

 flected round the arch of the aorta immediately beyond the attachment of the liga- 

 mentum arteriosum. Each nerve ascends in the neck behind the common carotid 

 artery, crossing either in front of or behind the inferior thyroid artery (see Yol. II, 

 p. 424), and lying in the groove between the trachea and oesophagus, to the lower 

 border of the cricoid cartilage, where it enters the larynx beneath the inferior con- 

 strictor muscle. Under cover of the ala of the thyroid cartilage, the nerve divides 

 into branches which supply all the intrinsic muscles of the larynx, with the exception 

 of the crico-thyroid. It likewise gives a few offsets to the mucous membrane below 



