332 FISHES. 



is extreme, and even some have attempted to deny its existence in 

 the chondropterygians ; but this is an error, for I have seen it very 

 distinctly in the Ray. In the Moon-fish, its ganglia are tolerably 

 large. It can be traced in the head as far as the nerves of the fifth 

 fair; but hitherto its junction with the sixth has not been made out 

 with sufficient distinctness. I believe, however, I have seen it in the 

 cod. 



The distribution of these different nerves is particularly remark- 

 able, on account of its resemblance to what takes place in the supe- 

 rior classes. Each pair has the same destination : tlie first supplies 

 the organ of smell ; the second, by its expansion, forms tlie retina 

 of the eye; the third, fourth, and sixth, go to the muscles of the eye. 

 each to the same muscles, as in quadrupeds, or birds : that is the third 

 supplying nearly all the muscles; the fourth the obliquus superior; 

 the sixth the abductor. The third also penetrates into the interior 

 of the globe, furnishing the filaments of its choroid membrane ; but 

 it appears not to form an ophthalmic ganglion, at least, it has not been 

 hitherto discovered. 



The fifth and eighth pairs are the most important, and those which 

 are distributed to the greatest number of different parts. 



The fifth comes out of the cranium through a foramen of the great 

 Aving, which is frequently divided into two by a small bony slip. Its 

 division into branches (pi. vi. fig. v.) occurs in its course, according 

 to the species ; but it uniformly gives, first, an opthalmic branch (a), 

 Avhich, ascending through the upper part of the orbit, goes to tlie 

 nostril, and is distributed to the adjacent parts to the top of the snout, 

 and to the intermaxillary bone ; second, a superior maxillary branch 

 (3) which passing beneath the eye, is distributed to the cheek, and 

 superior maxillary bone ; it sends a branch towards the nostril, and 

 anastomoses with the pterygo- palatine ; third, an inferior maxillary 

 branch (h) which is often only a division of the preceding, giving 

 twigs to the posterior part of the palate, and terminates at the lower 

 jaw, and at its dental canal ; frequently the threads of the palate are 

 supplied by a particular branch ; fourth, a pterygo-palatine branch (a), 

 which passing forwards, traverses the bottom of the orbit, under the 

 muscles of the eye, and following the direction of the vomer, passes 

 between this bone and the palatine, to terminate at the tip of the 

 snout, where it forms remarkable anastomoses with the sujjerior max- 

 illary ; fifth, an opercular branch (m), Avhicli traversing a canal of the 

 temporal bone, gives branches to the crotaphite, to the cheek, the 

 muscles of the operculum, to the operculum itself, penetrating late- 

 riorly, it joins in front witii the inferior maxillary nerve, and is dis- 

 tributed behind to the inferior opercular pieces, and to the branchios- 

 tegal membrane; and lastly, almost always sixth, a branch (C), 

 which, ascending towards the top of the cranium, unites with a brancli 

 of the eighth pair, (6) to pass out by a 'foramen of the parietal and 

 interparietal, and running along the back in (©), at the sides of the 

 dorsal fins, it receives twigs from all the intercostals, and furnishes 

 others to the muscles and rays of the fins. 



The course of this branch is superficial, until it dips under the small 

 external muscles of the rays. It has sometimes also superficial 

 branches Avhich descend to tlie anterior parts of the muscles of the 



