72 bulletin: museum of comparative zoology. 



marked tract posterior to the sensory root of nerve VII and, as in 

 the case of nerve X described below, the fine-fibered sensory root of 

 IX passes directly to this tract. What is stated regarding the motor 

 components of IX would apply equally well to nerve X. 



The combined roots pass out of the cranium by way of the recessus 

 scalae tympani between the ear capsule and the basoccipital bone. 

 Versluy's ('98, p. 180) general statement applies to Anolis on this 

 point: " Bei alien Lacertilia vera tritt demnach der Nervus glosso- 

 pharyngeus nicht durch ein eigenes Loch in der Paukenhohle, sondern 

 durch eine grosse Oeffung, welche die altern Autoren meist Fenestra 

 rotunda, die neuern Foramen jugulare externum genannt haben." 

 The root passes caudad underneath the mucous membrane to its 

 ganglion (Plate 7, figs. 20-23). This, the ganglion petrosumi (gn. IX), 

 as compared to the root ganglion of the vagus, has a much more distal 

 position on its root (Plates 2, 3), and probably represents the trunk 

 ganglion of X, inasmuch as there has been described in other forms 

 a root ganglion in addition to the petrosum. This ganglion occupies 

 the free space between the other organs on a level with the posterior 

 edge of the ear capsule (Plate 7, fig. 23). Its form is that of a uniform 

 o^'al, and it lies on the dorsomedian side of its fiber bundle, which it 

 incompletely surrounds. 



The coarse motor fibers may be traced directly through this bundle 

 and out into the nerve trunk beyond. They have the most ventral 

 position — that farthest removed from the ganglion cells — in their 

 course through the ganglion. The other fibers seem to be non-medul- 

 lated within the ganglion, but this appearance may be due to absence 

 of impregnation by the osmic acid. 



Between the ganglion of IX and the union of its main trunk with 

 XII there are connections with X and with the sympathetic system. 

 These vary in their position, as study of several series of sections has 

 shown, although certain relations are quite constant. In the series 

 plotted (Plates 2, 3) the anastomoses are relatively simple. The 

 frontal projection (Plate 2, fig. 4) is the only one that shows them. 

 These will be described first and the variations referred to later. 

 A very small bundle of fibers from the vagus (Plate 3, fig. 7, comn. 

 IX-X) enters the petrosal ganglion on its proximal side; these become 

 entirely mingled with fibers of IX so that the two are not separable 

 beyond the limits of the ganglion. When the bundle emerges from 

 the ganglion as the main trunk of IX, it shows' in cross section six or 

 eight coarse motor fibers, which have been followed from the motor 

 root above described; the rest are very fine fibers, but with sharply 



