146 MK. r. J. COLE ON THE STUUCTUliE AND ]MORPHOLOGY OF 



connected with the "palatine" division of the trigeminus. Goronowitsch (1888, 89) 

 largely confirms Van Wijhe. He mentions a lateral line anastomosis l)etween the vagal 

 and facial groups, as in Protopterus, and also a true Jacohson's anastomosis between the 

 palatine divisions of the Vlltli and IXth, as in Amia and Gadus. 



Pollard (1892, 160) correctly homologlses Jacohson's anastomosis in a table printed on 

 p. 398, and sliows in Taf. xxvii., fig. 7, a somewhat similar condition to that described in 

 Amia by Allis. The anastomosis is, however, continued forwards and unites also with 

 the trigeminus. There is no description or mention of the nerve in the text. The 

 anastomosis therefore in Polypterus agrees with the condition found in Acipenser 

 by Van Wijhe. In the fine work by Pinkus (1894, 157) on Protopterus anneclem a 

 lateral line anastomosis is described (outside the auditory capsule) connecting the root 

 and ganglion of the lateralis lateral line nerve with the common root of the superficial 

 ophthalmic and buccal lateral line nerves (cp. Goronowitsch). Jacohson's anastomosis i» 

 in much the same condition as in Gadus and Amia. The palatine branch of the IXth as 

 it passes forwards sends an anastomosing branch to the visceral or palatine branch of the 

 facial. There is no connection with the trigeminus. 



The anastomosis in Puna between the Vlllh and the IXth is apparently of a different 

 nature, though it also properly belongs to the IXth. Strong (1895, 204) says (p. 146) : — 

 " The other inner division of mixed fibres is the P. communicans ad facialem to the 

 R. hyomandibularis. Its final distribution is described in connection with the latter, 

 anU it lias there been found to be a general cutaneous nerve." (Italics mine.) The fact 

 that the nerve in Pana consists of somatic sensory fibres makes it impossihle to 

 homologise it with a true Jacohson's anastomosis. Strong, however, seems to have had 

 an inkling of the truth, for he remarks (p. 207) : " Furthermore, among the Fishes, the 

 palatine nerve would appear to be formed by a union of post- and pre-auditory nerves- 

 (Goronowitsch, Pollard). The development of the auditory organ has probably caused a 

 separation of nerves formerly more closely connected." 



In man the tympanic branch of the glossopharyngeal, or nerve of Jacobson, un- 

 doubtedly corresponds to the nerve called after it in the lower vertebrates. Its origin 

 from the petrosal ganglion, which seems to me to be morphologically comparable to the 

 " facial " or geniculate ganglion — that is, in connection with splanchnic sensory fibres — 

 at once suggests this. Unfortunately the composition of the tympanic nerve is, I believe, 

 not known in man. Its connection with the facial is partly by means of a small branch 

 which passes into the geniculate ganglion. This branch at least must be splanchnic 

 sensory, and is thus of the same constitution as Jacohson's anastomosis of the fish. 

 Its continuation, however, the small superficial petrosal nerve, is usually regarded as a 

 splanchnic motor nerve. Jacohson's anastomosis in man, therefore, seems to resemble 

 the same nerve of the fish in every essential detail. The exception, that it does not 

 directly anastomose with the great superficial petrosal ( = the palatinus facialis), is of 

 course of no morphological importance*. Dixon (1896, 61) has conclusively proved, 

 if such proof were wanting, that the nerve of Jacobson belongs to the glossopharyngeaL 



* App.'ircntly it docs so in tbo embryo. Cp. Dixon, p. 63.° 



