BRAIN AND CEREBRAL NERVES OF THE SKATE. 



659 



represented in fig. 322, wherein the reader will observe that the superior 

 oblique does not pass through a pulley, as is the case in the human 

 subject. 



Fig. 322. 



Brain and cerebral nerves of the Skate : a, olfactory ganglion ; b, c, cerebrum ; d, cerebellum ; 

 e, medulla spinalis ; g, the eyeball ; i, its cartilaginous pedicle ; k, olfactory sac ; 1, distribution 

 of the olfactory nerve. 



(1815.) It is extremely remarkable that even in fishes the muscles 

 of the eye have special nerves appropriated to them, and those precisely 

 the same as in the highest Mammalia. The third pair of nerves 

 animates them all, except the external rectus and the superior oblique, 

 and also sends off filaments to be distributed to the choroid, although no 

 ophthalmic ganglion has yet been discovered. The fourth pair is ex- 

 clusively appropriated to the superior oblique ; and the external rectus, 

 or abductor muscle, invariably receives its supply from the sixth pair. 



(1816.) To animals whose eyes are constantly washed by the water 

 in which they live, any lacrymal apparatus would obviously be super- 

 fluous ; and consequently, in the class before us, neither lacrymal gland 

 nor lacrymal puncta, nor even eyelids, properly so called, are ever 

 met with. 



(1817.) Behind the optic lobes of a fish's brain the ganglia from 

 which the other cerebral nerves emanate become confused into one mass, 



2u2 



