FISHES. 44^ 



was lemoved, and the sound had its full play upon the water, 

 the fishes seemed instantly to feel the change, and shrunk to the 

 bottom. From this we may learn, that fishes are as deaf as they 

 ore mute ; and that when they seem to hear the call of a whistle 

 or a bell at the edge of a pond, it is rather the vibrations of the 

 Bound that affect the water, by which they are excited, than any 

 sounds that they hear.* 



Seeing seems to be the sense fishes are possessed of in the 

 greatest degree ; and yet even this seems obscure, if we compare 

 it to that of other animals. The eye, in almost all fish, is 

 covered with the same transparent skin that covers the rest of 

 the head ; and which, probably, serves to defend it in the water, 

 as they are without eyelids. The globe is more depressed ante- 

 riorly, and is furnished behind with a muscle, which serves to 

 lengthen or flatten it, according to the necessities of the animal. 

 The crystalline humour, which in quadrupeds is flat, and of the 

 shape of a button-mould, in fishes is round as a pea ; or some- 

 times oblong, like an egg. From all this it appears that fish are 

 extremely near-sighted ; and that even in the water they can 

 see objects at a very small distance. This distance might very 

 easily be ascertained, by comparing the refraction of bodies in 

 the water with that formed by a lens that is spherical. Those 

 unskilled in mathematical calculations, will have a general idea 

 of this, from the glasses used by near-sighted people. Those 

 whose crystalline humour is too convex, or, in other words, too 

 round, are always very near-sighted ; and obliged to use concave 

 glasses, to correct the imperfections of nature. The crystalline 

 humour of fish is so round, that it is not in the power of any 

 glasses, much less of water, to correct their vision. This crys- 

 talline humour in fishes all must have seen ; being that little 



• It was well ascertained by Dr John Hunter that fishes possess the sen«o 

 of hi'siring, and that water is an excellent medium for the couveyauce of 

 8onnd. Their organ of hearing is placed on the sides of the skull, or the 

 cavity that contains the brain ; but, differing in this respect from that in 

 quadrupeds and birds, it is entirely distinct and detached from the skull. In 

 some fishes, as those of the ray kind, the organ of hearing is wholly s nr- 

 rounded by the parts containing the cavity of tlie skull ; in others, as the 

 salmon and cod, it is in part within the skull. In structure it is by no meaai 

 «o complicated as in the quadrupeds and other animals who live in the air. 

 Some genera, as the rays, have the external orifice very small, and placed 

 on the upper surface of the head ; but in others there is no external opening 

 whatever. 

 m. 2p 



