PISCES. 719 



line from the head to the tail. Sensation appears to be weak in almost all 

 the class, although some, as the eel^ possess irritability after being cut into 

 small portions. 



The nostrils in fishes are simple cavities or hollows at the point of the 

 snout, in the interior of which are disposed laminae in a radiated form. 

 These cavities are often divided into two compartments, and sometimes, as 

 in the lamprey, the two nostrils are united into one. The eye is possessed of a 

 very flat cornea, with but little aqueous humor ; but the crystalline lens is 

 almost globular, and very hard. In general, the eyes of fishes are large in 

 proportion to their size, and they are destitute of eyelids. The pupil, or the 

 opening by which light penetrates into the eye, varies much in form. In 

 the greater part of the species of which the eyes are vertical, anatomists 

 remark a singular disposition of the pupillary orifice, which presents the 

 fringes of the iris arranged in such a manner, as to dilate or contract, in order 

 to weaken or augment the quantity of light which enters the eye. In the 

 Pleuronectes, both eyes are on the same side of the dorsal line. The ear 

 consists of a sac which represents the vestibule, in which are suspended 

 bones of a stony hardness, and of three semicircular, membranous canals, 

 situate rather in the cavity of the cranium, than in the substance of its 

 walls, except among the Chondroptery gii. There is neither eustachian 

 lube, nor tympanum, and bones ; and the order Selachii have only an oval plate, 

 on a level with their head. It is probable that the vibrations of the water 

 may communicate a sensation analogous to that of sound. The sense of 

 taste in fishes cannot be delicate, as their tongue is often osseous, and 

 furnished with teeth or other hard covering ; they are destitute of salivary 

 glands, and the greater part swallow their food without maceration. 

 Neither is the sense of touch very acute, as in most, the body is covered 

 with scales, and in all, the organs of prehension are wanting. The cirri, or 

 filamentous, fleshy processes of some families, may, perhaps, supply the im- 

 perfections of their organs of touch. In the greater number of fishes, the 

 intermaxillary bone forms the margin of the upper jaw, having behind it 

 the maxillary or labial bone. The palatine arch, composed of the palate 

 bones, the two pterygoid processes, the zygomatic process, the tympanum, 

 and the squamous portion, forms, as in birds and serpents, a kind of interior 

 jaw, and furnishes behind, an articulation for the lower jaw, which has two 

 bones on each side ; but these pieces are reduced to the smallest number iu 

 the Chondropterygii. The teeth of fishes present many varieties. Some 

 have none at all, and in others the jaws are so hard that they form a kind 

 of solid beak ; in some, these teeth are pointed, edged, crenated, flat ; and 

 in others, they are placed on the lips, the jaws, the palate, the tongue, the 

 gullet, or in all these parts at the same time. The stomach is almost 

 always simple, and the intestinal canal short, as in carnivorous animals ; 

 the liver is very large ; and there is but one opening for rejected matters, 

 the milt of the male, and the ova of the female. 



