WILLARD: CRANIAL NERVES OF ANOLIS CAROLINENSIS. 75 
the fine fibers. It forms a bundle about two thirds the diameter of 
the main trunk of IX, which it joins to form the pharyngo-laryngeal 
_nerve (fig. K, Plate 2, fig. 4, pha-lar.). From this ramus are given off 
several small twigs to the constrictor muscle of the jugular vein (p. 44). 
These are fibers somewhat larger than the viscero-sensory fibers, but 
with extremely delicate myelin sheaths, and for this reason they were 
not discovered in the series of sections plotted; but in another series 
through this region (Fig. K), especially fixed, the innervation of these 
muscle fibers was determined. Of the three twigs shown in the draw- 
ing only one is given off from the superior laryngeus before its union 
with the ramus pharyngeus IX. 
It is important to note that these visceral muscle fibers (Plate 7, fig. 
23, co’st. un. j.1.), although striated, do not draw off any of the coarse 
fibers from the vagus, but are supplied by nerve fibers which are indis- 
tinguishable from the other fine fibers when mingled with them, but 
_ which nevertheless possess slight differences, as is shown when they 
are grouped together. We probably have in the innervation of this 
muscle a case analogous to that of the ciliary muscle, which primarily 
isnon-striated, but in the sauropsidais striated. Ifthe striated muscle 
| fibers surrounding the jugular vein have been differentiated from the 
| smooth muscle cells of the vessel wall; which are believed to. be 
| mnervated by non-medullated postganglionic neurons, the question 
| suggests itself as to what modification of the innervation has accom- 
| panied that of the musculature. As before stated the nerve fibers 
| show a slight medullation indicating to that extent a change from the 
| sympathetic type, but their continued course through the ganglion, 
| suggesting direct central origin, was not shown in the sections although 
| this was clearly demonstrated for the more heavily medullated fibers 
| passing into the pharyngo-laryngeal branch. Onuf and Collins (:00, 
|p. 174) describe two nuclei for efferent neurons of nerves IX and 
X in the mammals (cat). The dorsal glossopharyngeal and vagus 
_ nucleus, is, according to them, the nucleus of origin for the efferent 
sympathetic fibers carried in the roots of these nerves; the ventral, 
nucleus ambiguus, gives rise to the nerve fibers innervating muscles 
of visceral origin but of somatic function, derivatives of the striated 
gili-arch musculature of the fishes. The spinal accessory nerve, when 
resent, is exclusively of the latter type. The innervation of the 
special jugular vein muscle of Anolis suggests a condition intermediate 
between the sympathetic and the viscero-motor of the cerebro-spinal 
type. The slight development of this latter component in nerves IX 
and X made it impossible to establish this suggestion as a fact through 
| . analysis of the central terminations. 
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