Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29464/1039/
PISCES. 
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 caudal 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 fins, which represent 
the anterior extremities; and the two ventral 
fins, 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 wTould 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 with 
955 
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.”* 
“ Fishesarein 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.
        

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