FISH IN GENERAL. 73 



it. The distribution of the nerves is remarkably alike in 

 fishes and other animals of the superior classes, each pair 

 always preserving the same destination. The first passes 

 to the organ of smell; the second expands to form the 

 retina of the eye ; the third, fourth, and sixth are supplied 

 to the muscles of the eye ; each passing to the same as in 

 mammalia and birds ; that is the third nearly to all ; the 

 fourth to the superior oblique, and the sixth to the ab- 

 ductor muscle. The fifth pair passes out of the cranium 

 by the opening of the great ala, and divides into several 

 branches, one ophthalmic ; another superior maxillary ; a 

 third inferior maxillary ; a fourth pterygo-palatine ; a fifth 

 operculary ; a sixth branch unites on the cranium with one 

 of the eighth pair, and passes along the sides of the dorsal 

 fins : sometimes it sends other branches also over the trunk 

 towards the anal fin. The seventh pair of nerves belongs, as 

 in other vertebrated animals, to the auditory apparatus ; in 

 the eighth pair we can fully appreciate the constancy of 

 nature's plan in the distribution of each nerve : for the glosso- 

 pharyngeal passes out of the cranium, and is distributed upon 

 the first branchia, and about it, and passes to the tongue, 

 where it radiates ; the par vagum passing out at an opening 

 of the lateral occipital bone, sends branches to the three latter 

 branchiae, and to the inferior pharyngeals ; and the main nerve 

 continues to the pharynx, and follows the oesophagus to the 

 stomach, in its course sending off branches which spread over 

 the diaphragm. Thus we have the same distribution, only 

 modified by the respiratory organ being in a different situation 

 from the corresponding viscus in other vertebrated animals. 

 From the par vagum one or even two other nerves proceed, 

 not analogous to any in other classes ; the first passes to the 

 extremity of the tail, and in many species, after giving off a 

 superficial fibre, follows partly the lateral line, and passes 

 through the lateral muscles, receiving from the spinal nerves 



