76 bulletin: museum of comparative zoology. 



Bruner ( :07, p. 47) gives quite a detailed description of the innerva- 

 tion of the striated muscle of the jugular vein in reptiles. He finds 

 this muscle in Lacerta aqilis to be innervated by a number of nerve 

 twigs which are given off from the rami communicantes internus et 

 externus. The latter join the proximal end of the petrosal ganglion, 

 of nerve IX, which, in addition to its root is also joined by a communi- 

 cating ramus from ganglion X. Bruner applied stimulation methods 

 at various points in this nerve complex and thus determined the path 

 of the motor fibers to the "m. constrictor venae jugularis internae" 

 to be from the brain through the roots and root ganglion of nerve 

 X, across to the petrosal ganglion through the communicating ramus 

 between IX and X, and then cephalad along the rami communicantes 

 internus and externus to points where the " nervi tumefactores capitis " 

 are given off to the adjacent muscle surrounding the jugular vein. 

 According to Bruner the function of this musculo-nervous mechanism 

 is to contribute to the swelling of the cephalic veins and sinuses of the 

 head by blocking the return of blood through the internal jugular vein. 

 In Anolis (Fig. K) these "tumefactor" nerves show^ closest anatomical 

 relations to nerve X, the indirect course described by Bruner lieing 

 unnecessary because here the constrictor muscle lies relatively more 

 caudad than in Lacerta. Notwithstanding the fact that these nerves 

 are given off elsewhere, the ramus communicans X et IX occurs 

 quite constantly (see Plates 2, 3, absent Fig. A'). It is possible, then, 

 that this communicating ramus is an efferent sympathetic path not 

 exclusively related to the constrictor muscles of the jugular vein. 



After the union of the superior laryngeal ramus of X with that of 

 phar^^Tigeal IX the combined nerve (phx-lar.) joins XII in its course 

 to the ventral side of the pharynx. Beyond this point not all the 

 components of IX and X can be followed and accounted for positively 

 in their distribution. It seems certain, however, that the laryngeal 

 branch (phx-lar/), the first given off from XII after it reaches the ven- 

 tral side (figs. 5, 6), represents a large portion of this nerve, although 

 its smaller size establishes the fact that the trunk of XII still carries 

 some of the fine fibers. By using fine needles in dissection this laryn- 

 geal ramus can be split away from the main trunk of XII and thus it 

 may be demonstrated to represent the larger part of ramus pharyngo- 

 laryngeus, whose union with XII is mentioned above. 



1. Relations between Nerves IX and X. 



Preceding an account of the terminal rami of IX and X, a general- 

 ized summary of the relations of roots and main trunks of these two 



