1881.] -L-'^ [Stowell. 



of Ctl. thyi-oidea — A. larj^ngea superior is given off from A. carotidea 

 externa, just caudad of the origin of A. carotidea interna ; its course is, 

 therefore, at right angles with A. carotidea externa, 



iV. laryngeus externus lies ectad of the larynx ; it sends a pharyn- 

 geal ramulus cephalad and entad of A. laryngea superior (Fig. 7, SO), 

 which is distributed to M. constrictor pharyngis inferior, anastomoses with 

 the ojsophageal ramus of N. pharyngeus (Fig. 7, 31), gives terminal fila- 

 ments to Px. pharyngeus and the pharyngeal mucous membrane ; fila- 

 ments of this ramulus anastomose with N. crico-thyroideus and unite in 

 plexiform relation with N. sjanpathicus around A. thyroidea superior ; a 

 twig of this pharyngeal ramulus detached just dorsad of the hyo- thyroid 

 foramen, passes ventro-caudad to terminate in M. crico-thyroideus. This 

 ramus sends a laryngeal ramulus ventro-caudad which lies entad of M. 

 sterno-thyroideus, to which a few filaments are distributed, and is apposed 

 to A. laryngea inferior, which artery it accompanies to the cricoid 

 membrane as far as the ventrimeson (Fig. 7, 32) ; from this ramulus fila- 

 ments are given to M. crico-thyroideus. A caudal ramulus is also de- 

 tached whose course is dorsad of M. sterno-thyroideus and parallel with 

 its dorsal border to Cp. thyroideum (Fig. 7, 33) ; it gives filaments to M. 

 crico-thyroideus and anastomotic filaments to N. descendens noui, which 

 it joins opposite the origin of A. thyroidea superior. 



N. laryngeus internus enters the hyo-thyroid foramen and divides into 

 a cephalic and a caudal offset: the cephalic offset (Fig. 7, 34.) accom- 

 panies the ental portion of A. laryngea superior, pierces M. thyro-arytae- 

 noideus to which numerous filaments are distributed, takes its cephalic 

 course obliquely toward the ventrimeson and perforates the thyro-hyoid 

 membrane 3 mm. laterad of the meson. Terminal filaments of this offset 

 supply the epiglottis (Fig. 7, 36), thearytaeno-epiglottidean folds (Id. 37). 

 the laryngeal glands (Id. 35), and the mucous membrane of the larynx 

 (Id. 35, a). A twig given from the cephalic offset, 2 mm. peripherad of 

 the foramen, passes entad of the apposed artery (A. laryngea superior 

 entalis) and joins the caudal offset 3 mm. cephalad of the caudal border of 

 Ctl. thyroidea (Fig. 7 and 8, 39). 



The caudal offset lies closely apposed to the ental surface of Ctl. 

 thyroidea (Fig. 7 and 8, 38); its first twig is sent dorso-caudad and termi- 

 nates upon M. crico-arytseiioideus lateralis, M. arytaenoideus and M. con- 

 strictor pharyngis inferior (Fig. 8, 4.O); anastomotic filaments join in plex- 

 iform relation with its dextral homologue and with the pharyngeal and 

 oesophageal plexuses. The principal portion of the caudal offset at its union 

 with the twig from the cephalic offset gives off radiating filaments upon 

 the ectal surface of the arytaenoid muscles which constitute a multiple 

 palmate plexus (Fig. 8, 4I.); a twig passes dorsad of the articular facet of 

 Ctl. cricoidea and joins N. laryngeus inferior (fig. 8. 42). Near the union 

 of the twig and the offset, entad of cephalic border of Ctl. cricoidea several 

 filaments penetrate M. crico-arytaenoideus and are distributed upon the 

 mucous membrane of the larynx. 



