SYMPATHETIC GANGLIA 253 



of the great superficial petrosal nerve and enter this tract. The 

 majority of the nervous elements in this fiber-tract, however, 

 probably are cells which have advanced cephalad from the 

 superior cervical ganglion. 



As early as the fibers emerging from the sympathetic plexus 

 surrounding the carotid artery may be traced cephalad, the cells 

 of nervous origin accompanying them are relatively numerous. 

 Some of these cells soon become aggregated into a ganghonic mass 

 which represents the anlage of the otic ganglion. This ganglionic 

 anlage arises but a short distance cephalad of the geniculate 

 ganglion. As development advances, it becomes removed some- 

 what farther cephalad until it lies mesial to and shghtly caudad 

 of the origin of the mandibular division of the trigeminal nerve. 

 Figure 16 illustrates the relationships of the otic ganghon to the 

 great superficial petrosal nerve and the sympathetic plexus sur- 

 rounding the carotid artery, as observed in sagittal sections of an 

 embryo of the chick during the seventh day of incubation. The 

 relationships of the otic ganglion to the superior cervical ganglion 

 and the VII and V cranial nerves are illustrated (hagrammatically 

 in figure 17. 



No fibrous or cellular communications could be observed, dur- 

 ing the early stages of development, between the otic ganglion and 

 the mandibular division of the trigeminal nerve or the Gasserian 

 ganglion. The cells which take part in its development are derived 

 primarily from the superior cervical and the geniculate ganglia. 



SjjhenopaJotine ganglion 



The great superficial petrosal nerve may early be traced, in 

 embryos of the chick, from the geniculate ganglion into the max- 

 illary region where it terminates in the loosely aggregated anlage 

 of the sphenopalatine ganglion in proximity with the olfactory 

 epithelium (fig. 18, sphg). This ganglion receives fibrous com- 

 munications also from the maxillary division of the trigeminal 

 nerve. This division of the trigeminal is a relatively slender nerve 

 containing relatively few cells of nervous origin. There is no 



