174 FRED W. STEWART 



soon after, gives a fine anastomotic branch to the trigeminus, 

 and ganglion cells are found along these fibers. These are, 

 i eedless to say, of scanty number. Koch ('16) and Rhinehart 

 ('18) have reported the presence of sympathetic fibers in the 

 abducens nerve. As regards other outgrowths from the cervical 

 sympathetic, we must consider those fibers passing toward the 

 ierritory of the middle ear and entering into the formation of 

 the tympanic plexus. They have been given especial attention 

 in view of their later involvement with fibers of the glossopharyn- 

 geal nerve, and in view of the possibility of confusing ganglion 

 cells originating from different sources. In fifteen-day embryos 

 strands from the internal carotid nerve, cephalad of the superior 

 cervical sympathetic ganglion, enter the dorsal pharyngeal region 

 and become lost in the mesenchyme over the region of the first 

 pharyngeal pouch. The strands are two in number, and both 

 have been seen to contain ganglion cells, in each case near the 

 origin of the strand. These strands are recognized as the earliest 

 appearance of the superior and inferior caroticotympanic nerves. 

 In sixteen-day embryos the posterior of the two strands has 

 become relatively much larger and numerous ganglion cells are 

 to be noted (fig. 1); seventeen-day embryos show a complete 

 sympathetic anastomosis about the cartilaginous otic capsule. 

 Subsequent to sixteen-day stages there apparently occurs some 

 mixing of glossopharyngeal fibers with fibers from the cervical 

 sympathetic, but the origin of certain ganglion cells of the 

 tympanic plexus apart from any contribution via the glosso- 

 pharyngeal seems clear. In concluding this section we may 

 state that in addition to the ganglia of the carotid plexus and 

 its extensions, a portion of the ganglia of the tympanic plexus 

 belong with forward extensions from the superior cervical sympa- 

 thetic ganglion. 



Vagus port ion of the sympathetic 



Coming now to the question of sympathetic ganglia related 

 drvelopmentally to the cranial nerves, it is perhaps most con- 

 venient to consider first the vagus group. Previous attempts 

 have been made to show that the vagus plays a part in the 



