86 bulletin: museum of comparative zoology. 



By examination into the component character and central relations 

 of this nerve, where it exists, it is found to be similar to those viscero- 

 motor components of X and IX which innervate striated muscles 

 (Johnston, :06, p. 203), such as the laryngeal muscles. These all 

 have their cells of origin (in the higher vertebrates at least) in a portion 

 of the viscero-motor column ventrally separated from the rest and 

 known as the nucleus ambiguus. While the motor nuclei of this 

 region of the hind brain have been incompletely identified in Anolis, 

 microscopic study has fully demonstrated that IX and X contain a 

 very limited number of components such as innervate the laryngeal 

 muscles and that these all pass ventrally with XII, which gives off 

 no branches that cannot be directly traced to muscles of the ventral 

 head region. 



It still remains to be demonstrated whether there is a caudally 

 extended motor nucleus ambiguus which contributes fibers to the spinal 

 nerves innervating the muscles originally supplied by the accessorius. 

 In the absence of such a relation, it would then be a question whether 

 the trapezius muscle in Anolis is homologous to the one so named 

 elsewhere. 



• The apparent absence in Anolis of anything corresponding to the 

 spinal accessory is an anomolous condition in reptiles, because, even 

 making allowance for many misinterpretations depending on gross 

 dissections, the universal mention of such a nerve in the literature 

 bearing on reptilian anatomy would indicate a greater development 

 of the vago-accessorius group than is shown in Anolis. Fischer ('52, 

 p. 62) finds that the condition first described by Bischoff ('32) is 

 realized in all the forms he studied, viz. that from 5 to 9 fine bundles, 

 generally increasing in strength posteriorly, arise along an irregular 

 line extending from the level of the second cervical nerve to the origin 

 of the vagus. All these root bundles assemble into one trunk, which 

 generally fuses with the vagus. In two species of the genus Salvator, 

 however, this trunk remains separate, although it passes out through 

 the same foramen with the vagus. This independent course of the 

 accessorius was also described by Bendz ('43) for Chdonia my das. 

 What Fischer calls the accessorius includes, in addition to the ramus 

 externus, fibers which have a distribution with the laryngeal branch of 

 the vagus, or with the ramus recurrens vagi, or with both. The 

 ramus externus, which by gross methods is the only portion of the 

 accessorius that can be followed to its distribution, was not found 

 by him in all forms. It was absent in Chamaeleo vulgaris and Agama 

 spinosa. No mention was made as to whether there was a correlated 



