CRANIAL SYMPATHETIC GANGLIA IN THE RAT 197 



the nerve ends anteriorly in a rich, though diffuse, plexus of 

 strands. Similar conditions are approached in 15- and 16-mm. 

 pig embryos. As the number of neuroblasts among the fibers 

 of the ramus palatinus VII is increased, the forward and outward 

 growth of the sphenopalatine ganglion brings it into relation 

 with palatine branches of the maxillary nerve; these branches 

 never, so far as I am able to determine, possess the appearance 

 of a migration path. The palatine branches of the maxillary 

 nerve traverse the sphenopalatine ganglion in fourteen and one- 

 half day rat embryos ; the main mass of the ganglion lies posterior 

 to these palatine branches, diffusely scattered along the entering 

 fibers of the ramus palatinus VII. In fifteen-day rat embryos 

 (fig. 32) the sphenopalatine ganglion is an elongated, very diffuse 

 structure, and at slightly later periods, its growth brings it into 

 direct contact with the main trunk of the maxillary division of 

 the trigeminus; with the ganglion well formed, it is difficult to 

 judge whether or not it receives subsequent additions from the 

 semilunar ganglion; so far as I am able to determine, it does 

 not. Still later stages find the sphenopalatine ganglion directly 

 continuous with the semilunar ganglion (fig. 33), with, neverthe- 

 less, a clear line of division between their respective cell elements. 

 The development of the sphenopalatine ganglion in the pig is 

 very similar in its early stages (15 to 18 mm.) to that of the rat; 

 later stages have not been followed. It has been traced from a 

 diffuse collection of neuroblasts amid the anterior terminations 

 of fibers of the ramus palatinus VII (figs. 34 and 35) to a relatively 

 compact structure in contact with the main ramus maxillaris V. 

 Its first appearance is well mediad to the palatine branches of 

 the maxillary nerve. In concluding this section on the develop- 

 ment of the sphenopalatine ganglion, the fact should be empha- 

 sized that in the turtle and in the chick Kuntz('14) has derived 

 the ganglion from cells migrating outward along the great super- 

 ficial petrosal nerve. The early diffuse character of the ganglion 

 which. he describes in these forms is quite suggestive in view of 

 my own observations on conditions found in the rat and the pig. 

 Certainly, one would suppose that such a structure as the spheno- 

 palatine ganglion would possess fundamentally the same mode 

 of origin in all forms in which it occurs. 



