FISHES, Rat 
what anglers now know to be true, that these active chasseurs of the 
deep saw far and very clearly.* 
If fishes have great eyes, they have, on the other hand, very small 
ears. This crgan, it is found, has no exterior opening. It forms a 
"A ii | 
; Fig. 351.—A Fish’s Eye. Fig. 353.—Teeth of the Carp. 
z, crystalline lens ; ce’, cornea ; 2, posterior 
chamber ; ¢, optic nerve. 
cavity in the interior of the cranium, which is far from presenting the 
complicated structure of the ear in mammals and birds. In spite, 
* Dr. Fripp’s theory of the properties of the fish’s eye is very plausible. 
Ist. That the fish’s eye in its normal state is arranged for the vision of near 
objects, and that the great refractive power of a prolate spheroid lens, such as 
exists in the fish, is adequate to the production of a picture at short focal distances, 
even with rays of light passing through so dense a medium as water. 
2nd. That there is no accommodation of the fish’s eye for extended limits or 
vision. 
3rd. That the passive state of the fish’s eye, being that in which it is enabled 
to see objects near and at moderate distance, no active or physiological change for 
accommodation of sight for distant objects takes place or seems necessary. 
The dioptric arrangement, being the reverse of that which obtains in animals 
where ‘‘accommodation” is observed, and in whom the Passive stace is that of 
vision, arranged for distant objects, while the actéve state is that of vision accom- 
modated at will for near objects. 
4th. That the vascular distribution of the choroid vessels has no relation to any 
movement of the lens, or change of its shape, but is arranged to meet the changes 
of static condition of the circulating fluid, and of dynamic force exerted by the 
heart under varying pressure from without; and that by such an arrangement, 
protection to the delica’e tissues of the eye is afforded by a compensating balance 
between the tension of the blood within the vessels and the external pressure 
exerted upon them. 
II 2 
