660 MR FRANK J. COLE ON THE 



of an)' great importance, (c) cannot obtain in Fishes, and (e) can only be represented by 

 a ventral continuation on to the pharynx. The chorda t}onpani is in an exceedingly 

 interesting condition in man,* and seems to exactly correspond to the condition described 

 in Amphibia by Strong. The great superficial petrosal corresponds, as first shown by 

 Stannius, and confirmed by Gegenbaur and Ewart, to the palatine of fishes; and 

 according to many observers the chorda tympani of man derives a great part at least of 

 its fibres from the base of the great superficial petrosal, and thus, as in Amphibia, only 

 accompanies the post-branchial division of the faded (main trunk of the facial of man). 

 No one who has examined Professor Thane's diagram of the facial in Quain's Anatomy 

 can fail to notice the fundamental resemblance between it and that of larval Amphibians 

 and Fishes (cp. particularly Strong, p. 186). I therefore suggest that the facial of man 

 divides, as in Fishes, into the following 3 fundamental branches: (1) great superficial 

 petrosal ( = palatine or visceral) ; (2) chorda tympani ( = prse-spiracular, arises from base 

 of l) ; (3) main trunk (= post-branchial). From the fact that the chorda tympani of 

 Mammals passes morphologically under the tympanum, and as the spiracle of fishes is 

 considered by some to be equivalent to the tympanum + Eustachian tube of Mammals, 

 it has been argued that any representative of the chorda in fishes should have similar 

 relations to the spiracular cleft. This, however, is assuming (l) that the spiracle has 

 been correctly homologised in Mammals (which is still a somewhat open question) ; and 

 (2) that, on the conversion of the spiracle, the prse-branchial nerve did not do what we 

 know it has done in Amphibia, i.e., accompany the post-branchial, and thus become a 

 topographical but not a morphological post-branchial nerve. We are now, after a 

 consideration of the chorda in Mammals, in a position to define the characteristics of 

 its representative in Fishes. These are : (1) it should arise from the base of the palatine, 

 i.e., the facial should give off its 3 fundamental branches at the same place, and that 

 place above the hyomandibular cleft ; (2) should enter into branchial relations with the 

 mandibular arch, and consist essentially of splanchnic sensory fibres ; and (3) should 

 have the representative of a lingual branch, i.e., should be continued ventrally on 

 to the pharynx in the region of the tongue. It is obvious that the nerve I have 

 described in Chimsera supplies all these conditions ; and as we have previously seen that 

 it represents the prse-spiracular nerve of other fishes, we may conclude that this latter 

 nerve is the representative of the chorda tympani of Mammals. 



(5) In all the cartilaginous fishes that I have examined the prse- and post- branchial 

 divisions of the IXth and Xth have been united by a stout commissure. I have already 

 described a similar commissure between the chorda and post-branchial divisions of the 

 facial of Chimsera. 



(6) Marshall, in describing the development of the chick,t says that the facial arises 

 as a " large hyoidean or post-branchial branch, which runs along the hyoid arch, 

 and a smaller mandibular or prse-branchial branch, which runs forwards over the 



* Despite certain assertions to the contrary, the chorda tympani of Mammals must be regarded as distinctively 

 a branch of the Vllth (cp. Dixon, infra). t Vert. Emb., p. 266. 



