CRANIAL SYMPATHETIC GANGLIA IN THE RAT 



189 



ramus palatinus (ramus tympanicus or Nerve of Jacobson). 

 These divisions will be considered in the order named. 



In 5.5-mm. embryos (gray rat) the lingual division of the 

 glossopharyngeus may be traced into the floor of the pharynx 

 as an exceedingly cell-rich strand (fig. 26). It is composed of 

 cells quite closely resembling elements found within the ganglion 

 petrosum, and some difficulty is experienced in distinguishing 

 the exact limits of the ganglion. The contrast between the 

 glossopharyngeal nerve and the hypoglossal, a purely motor 



Fig. 10 Rat embryo, 15f days, vom Rath's technique. Similar cells along 

 finer branches of the ramus lingualis IX in the tongue. Projection drawing, X 500. 



nerve, is very marked (fig. 26). The latter nerve is practically 

 free from accompanying cell elements. Slightly later stages 

 (fourteen and one-half and fifteen-day albino rats) show cluster- 

 ings of elongate cells, similar to those found in the early vagus 

 trunk, along the glossopharyngeal nerve as it enters the tongue 

 (fig. 9), and shortly aftenvard they are evident in the finer 

 lingual branches of the nerve (fig. 10). As yet no definitive 

 neuroblasts are evident; the writer believes that the definite 

 test for the presence of a developing ganglion cell must be, as 

 in the case of the vagus, the development of the characteristic 



