CRANIAL SYMPATHETIC GANGLIA IN THE RAT 199 



of the ganglion refers to pig embryos of 13- to 16-mm. length. 

 Kuntz' observation on the time of union of the chorda with the 

 lingualis would agree with my own findings in the pig; the two 

 strands have not yet united in an 11-mm. embryo, but from the 

 relative positions of the nerves, the fusion must occur very soon 

 after. In my next available series (15 mm.) the union has oc- 

 curred and the ganglion is present, at least as closely related to 

 the chorda as it is to the lingualis. In the rat, the submaxillary 

 ganglion does not make its appearance until after the fusion of 

 the chorda and lingualis has occurred. I have been able to 

 examine nine series showing the chorda tympani previous to 

 this period. It resembles closely in structure the early palatine 

 rami (VII and IX) and is proportionally more cellular in character 

 than is the ramus maxillaris. In fourteen-day rat embryos the 

 chorda has united with the lingualis, although at this period the 

 combined trunk is more largely chorda ; the submaxillary ganglion 

 has not been found at this stage. Later, when the structure does 

 appear, it lies on that aspect of the combined chorda-lingualis 

 trunk where one would from previous relations recognize 

 mostly chorda fibers. In fifteen-day embryos the ganglion sur- 

 rounds the combined trunk, but again is mainly on the chorda 

 side; the evidence is of course purely circumstantial, and some 

 account must be taken of the fact that the 'chorda side' of the 

 nerve is likewise that aspect nearest the developing submaxillary 

 gland. Nevertheless, the similarity between the chorda and the 

 ramus lingualis IX and the fact that the more posterior lingual 

 ganglia arise in connection with the latter are strongly suggestive 

 of a chorda origin of the submaxillary ganglion. The greater 

 proportion by far of the small sympathetic ganglia of the tongue 

 are formed as a continuance of the same migration which gives 

 rise to the submaxillary ganglion and the closely allied sublingual 

 ganglion. This formation of small lingual ganglionic masses 

 apparently occurs fairly late; in seventeen-day rat embryos 

 ganglion cells are found in virtually continuous strands, from 

 points on the entering chorda-lingualis trunk into the mesen- 

 chyme surrounding submaxillary and sublingual glands, along 

 the submaxillary duct, and upward into the tongue, where they 



