80 bulletin: museum of comparative zoology. 



others IX is independent of both X and XII; these conditions have 

 significance in determining the probable source of the terminal 

 branches in such a form as Anolis, where these branches cannot be 

 followed back through the combined trunk; they will be referred 

 to again in the account of the terminal distribution of IX and X. 

 Since nerve X is larger than IX in all the forms described, its ganglia 

 have been more regularly found than those of IX. The trunk gan- 

 glion of X {gn. nd.) is a more constant feature than its root ganglion 

 {gn. rx. X, gn. X), having been described for all species hitherto 

 studied. On the other hand, the root ganglion, such as is found in 

 Anolis, has been definitely identified as an independent ganglion in 

 only three forms. 



3. Terminal Distribution of Nerves IX and X. 



From the foregoing account it is seen that all the components of 

 IX and X (excepting the rami to the jugular vein) are distributed 

 peripherally from three rami. (1) Jacobson's anastomosis, carrying 

 viscero-sensory fibers to VII; (2) Pharyngo-laryngeal, carrying the 

 superior laryngeal branch of X and the pharyngeal branch of IX, 

 both of which include viscero-sensory and viscero-motor fibers; 

 (3) ramus visceralis, carrying viscero-sensory fibers of X. To what 

 extent efferent sympathetic fibers may be carried in any of these rami 

 could not be determined. 



(1) Jacobson's anastomosis. This term is here used for the com- 

 municating ramus {comn. i.) between IX and VH, which joins the 

 base of the ramus palatinus. As the term is generally employed it 

 is restricted to a connection between these points, which carries a 

 viscero-sensory palatine branch from IX to be distributed with pala- 

 tine VII, and also innervates the mucous surfaces caudad to VII. 

 Because of the development of the sympathetic system of the head, 

 the main trunk of which takes this course, it is difficult to determine 

 to what extent this is a true viscero-sensory branch. In Anolis two 

 points on VII are connected with IX, usually at the distal end of the 

 petrosal ganglion. This connection is often so slight that it is lost 

 sight of in the more evident fact of the direct passage of this sympa- 

 thetic bundle caudad to its ganglion. It is always large enough, 

 however, to give rise to all the meduUated fibers contained in the 

 internal communicating branch, which is the one having the position 

 of Jacobson's anastomosis. Whether it docs give rise to them cannot 

 be stated. It can be stated that if Jacobson's anastomosis (as re- 

 stricted) exists in Anolis, it contains very few viscero-sensory elements. 



