PISCES. 



955 



PISCES. (Eng. Fishes; Fr. Poissons; 

 Germ. Fische-) The lowest class of the ver- 

 tebrate division of the animal kingdom, em- 

 bracing numerous oviparous races of beings 

 fitted by their organization to live only in 

 water, and consequently they are the appro- 

 priate inhabitants of the ocean and of inland 

 streams and lakes. Being strictly aquatic in 

 their habits, Fishes respire through the medium 

 of the element in which they live by means of 

 gills or branchiae, that are connected with a 

 framework of bony or cartilaginous arches situa- 

 ted on the sides of the neck, to which the water 

 obtains free access, generally passing in at the 

 mouth and escaping through lateral openings 

 situated behind the head. Their heart is bilocu- 

 lar, and consists of an auricle and ventricle, 

 which, receiving the venous blood from the sys- 

 tem, propel it over the respiratory surface, 

 whence it is collected into an arterial trunk, the 

 aorta, by which it is distributed over the body 

 without the intervention of a systemic heart. 

 Their blood is of very low temperature, and their 

 bodies are generally covered with scales of va- 

 rious kinds, whereby they are preserved from 

 maceration in the surrounding water, and fitted 

 to glide smoothly through the fluid medium 

 wherein they live. Their principal instrument 

 of progression is their tail, which is generally 

 expanded into a broad fin, that strikes the 

 water by alternate lateral movements. Besides 

 this candid fin others are frequently met with 

 situated along the median line of the body, to 

 which the names of dorsal and anal fins have 

 been appropriated accordingly as they are situa- 

 ted upon the back or behind the anal outlet of 

 the body. The position of these azygos fins is 

 vertical, and their use to a fish is similar to that 

 of the keel or of the helm to a ship. The repre- 

 sentatives of the anterior and posterior extremi- 

 ties of other Vertebrata likewise take the form 

 of fins, and are only fitted for progression in the 

 water : these are generally four in number, 

 namely, the two pectoral Jins, which represent 

 the anterior extremities; and the two ventral 

 Jins, corresponding with the posterior limbs of 

 Quadrupeds. Great variety is met with both in 

 the number and position of these locomotive 

 members; generally all four are present; fre- 

 quently one pair is deficient, and sometimes 

 they are altogether wanting. In situation they 

 likewise vary, more especially the ventral pair, 

 which in some races, instead of being behind, 

 are situated in front of the abdomen, in con- 

 nection with the scapular apparatus, and even 

 anterior to the pectoral fins. 



In the construction of their cerebral system 

 Fishes evidently stand lowest in the vertebrate 

 scale, and every part of their economy indicates 

 their inferiority to Reptiles, Birds, and Mam- 

 mals. 



The general attributes of Fishes and their 

 relative position in the animal scale are so well 

 laid down by their great modern historian, 

 Cuvier, that it would be presumptuous not to 

 give his own words. 



" Breathing by the medium of water, that 

 is to say, only profiting by the small quan- 

 tity of oxygen contained in the air mixed witli 



the water, their blood remains cold; their vita- 

 lity, the energy of their senses and movements 

 are less than in Mammalia and Birds. Thus 

 their brain, although similar in composition, is 

 proportionally much smaller, and their external 

 organs of sense not calculated to impress upon 

 it powerful sensations."* 



" Fishes are in fact, of all the Vertebrata, those 

 which give the least apparent evidence of sensi- 

 bility. Having no elastic air at their disposal, 

 they are dumb, or nearly so, and all the senti- 

 ments which voice awakens or entertains they 

 are strangers to. Their eyes are as it were mo- 

 tionless, their face bony and fixed, their limbs 

 incapable of flexion and moving as one piece, 

 leaving no play to their physiognomy, no ex- 

 pression to their feelings. Their ear, enclosed 

 entirely in the cranium, without external concha, 

 or internal cochlea, composed only of some sacs 

 and membranous canals, can hardly suffice to 

 distinguish the most striking sounds, and, 

 moreover, they have little use for the sense of 

 hearing, condemned to live in the empire of 

 silence, where every thing around is mute." 



" Even their sight in the depths which they 

 frequent could have little exercise, if most of 

 them had not, in the size of their eyes, a means 

 of compensation for the feebleness of the light; 

 but even in these the eye hardly changes its 

 direction, still less by altering its dimensions 

 can it accommodate itself to the distances of 

 objects. The iris never dilates or contracts, and 

 the pupil remains the same in all intensities of 

 illumination. No tear ever waters the eye no 

 eyelid wipes or protects it it is in the Fish but 

 a feeble representative of this organ, so beau- 

 tiful, so lively, and so animated in the higher 

 classes of animals." 



" Being only able to support itself by pursuing 

 a prey which itself swims more or less rapidly, 

 having no means of seizing it but by swallow- 

 ing, a delicate perception of savours would have 

 been useless, if nature had bestowed it; but 

 their tongue almost motionless, often entirely 

 bony or coated with dental plates, and only 

 furnished with slender nerves, and these few in 

 number, shews us that this organ also is as 

 obtuse as its little use would lead us to ima- 

 gine it." 



" Their smell even cannot be exercised so 

 continually as in animals which respire air and 

 have their nostrils constantly traversed by 

 odorous vapours." 



" Lastly, their touch, almost annihilated at the 

 surface of their body by the scales which clothe 

 them, and in their limbs by the want of flexibility 

 in their rays, and the nature of the membranes 

 investing them, is confined to the ends of their 

 lips, and even these in some are osseous and 

 insensible." 



" Thus the external senses of Fishes give them 

 few lively and distinct impressions. Surround- 

 ing nature cannot affect them but in a confused 

 manner; their pleasures are little varied, and 

 they have no painful impressions from without 

 but such as are produced by wounds." 



" Their continual need, which, except in the 



* Cuvier and Valenciennes, Histoire des Poissons. 



