82 bulletin: museum of comparative zoology. 



The main trunk passes fon\-ard, gi\dng off two more branches to the 

 mucous membrane (Plate 2, fig. 5) before turning abruptly across 

 the ventral floor of the larynx to form an H-shaped anastomosis with 

 the same nerve of the opposite side (Plate 2, fig. 5, an'stm. lar.). The 

 chiasma is not a complete one; hence each muscle of the larynx is 

 stimulated through motor fibers from both sides of the brain. 



The muscles of the larynx consist of an outer longitudinal (dilator) 

 and an inner transverse (constrictor) pair, (Plate 4, fig. 11, lar. Ig. and 

 co'st. lar.). They are innervated exclusively from the coarse fibered 

 elements carried in the pharjugo-laryngeus IX and X. Attention 

 is called to the fact that this motor innervation may be from IX, from 

 X, or from both. There is no possibility of determining in Anolis, 

 except experimentally, which nerve has given up its fibers to the cerato- 

 hyoideus muscle. If dissections may be trusted on this point, the 

 condition as described by Watkinson ( ;06) in Varanus would support 

 the view that the fibers innervating the cerato-hyoideus (hyoglossus) 

 muscle are from IX. In Varanus IX does not anastomose with XII 

 and does not appear to combine with X in a manner corresponding 

 to the condition in Anolis. In the former the nerve described as IX 

 innervates the cerato-hyoideus muscle as it crosses the ventral face 

 of that muscle. There are more proximal anastomoses, however, 

 making possible some combination of the fibers of IX and X as in 

 Anolis; so, in the absence of microscopic observation, any conclusion 

 must be tentative. 



The larjTigeal anastomosis is quite generally mentioned where the 

 innervation of this region is described in higher vertebrates. The 

 ramus recurrens X is usually described as entering into this "sling" 

 and joining in the motor innervation. In Anolis, however, the ramus 

 recurrens takes no part in the sling, although the terminal ramus of 

 this nerve passes through the longitudinal laryngeal muscle (Plate 2, 

 Fig. 5, lar. Ig.) to reach the dorsal free edge of the laryngeal cartilage, 

 where its fibers may be seen turning in to innervate the epithelium 

 of the lar;>Tix (Plate 2, fig. 5, rcr. X). 



(3) Ramus visceralis (vsc. X). This is the name given the main 

 trunk of the vagus after the superior lar>Tigeal nerve is given off. 

 It is a fine-fibered bundle, which closely resembles the main sympa- 

 thetic, with which it has a parallel course across the dorsal side of 

 the thymus gland. It bears the large trunk ganglion {gn. nd.) in 

 its course and then gives off to the mucous membrane sensory 

 branches, which correspond to the posterior laryngeal, and also the 

 ramus recurrens X. In the series plotted the sections are not carried 



