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$atttrc. 233 



, Their senses are incapable of making any 

 | nice distinctions ; and they move forwards 

 in pursuit of whatever they can swallow, 

 conquer, or enjoy. A craving desire of food 

 seems to give the ruling impulse to all their 

 motions. This appetite impels them to en- 

 counter every danger ; and to their rapacity 

 no bounds appear prescribed. Even when 

 taken out of the water, and almost expiring, 

 they greedily swallow the very bait which 

 lured them to destruction. Their digestive 

 1 powers seem, in some measure, to increase 

 ! with the quantity of food they consume ; and 

 ] i a single pike has been known to devour a 



I hundred roaches in three days. The amaz- 

 ing digestive faculties in the cold maws of 

 i! fishes have justly excited the curiosity of 

 I' i philosophers, and have effectually over- 

 ; turned the system of those who maintain 

 that the heat of the stomach is a sufficient 

 instrument for digestion. The truth seems 

 to be, that there is a power of animal as- 

 similation lodged in the stomachs of all 

 creatures, which we can neither describe nor 

 define, converting the substances they swal- 

 low into a fluid adapted for their peculiar 

 support. This is effected neither by tritu- 

 ration, by warmth, by motion, by a dissolv- 

 ing fluid, nor by their united efforts ; but by 

 some principle in the stomach yet unknown, 

 which acts in a manner very different from 

 all kinds of artificial maceration. The food 

 taken into the stomach is often seen, though 

 nearly digested, still to retain its original 

 form ; and, in fact, is ready for a total dis- 

 solution, while to the eye it appears yet un- 

 touched by the Ibrce of the digestive powers. 

 But though the appetites of Fishes are in- 

 satiable, no animals can endure the want of 

 food so long. 



Professor Owen, in his ' Lectures on Com- 

 parative Anatomy,' observes, " A few species 

 retain the primitive vermiform type, and 

 have no distinct locomotive members ; and 

 these members, in the rest of the Piscine class, 

 are small and simple, rarely adapted for any 

 other function than the propulsion or guid- 

 ance ot the body through the water. The 

 form of the body is, for the most part, such 

 as mechanical principles teach to be best 

 adapted for moving with least resistance 

 through a liquid medium. The surface of 

 the body is either smooth and lubricous, or 

 is covered by closely imbricated scales, rarely 

 defended by bony plates or roughened by 

 hard tubercles ; still more rarely armed with 

 spines. The central axis of the nervous sys- 

 tem presents but one partial enlargement, 

 and that of comparatively small size, at 

 its anterior extremity, forming the brain, 

 which consists of a succession of simple gan- 

 glionic masses, most of them exclusively 

 appropriated to the function of a nerve of 

 special sense. The power of touch can be 

 but feebly developed in fishes. The organ 

 of taste is a very inconspicuous one, the 

 chief function of the frame-work supporting 

 it, or the hyoidean apparatus, relating to the 

 mechanism of swallowing and breathing. 

 Of the organ of hearing there is no outward 

 sign; but the essential part, the acoustic 

 labyrinth, is present, and the semicircular 

 canals largely developed within the laby- 



1 rinth is without cochlea, and Is rarely 

 provided with a special chamber, but is 

 lodged, in common with the brain, in the 

 cranial cavity. The eyes are usually large ; 

 but are seldom defended by eyelids, and 

 j never served by a lachrymal organ. The 

 ; alimentary canal is commonly short and 

 simple, with its divisions not always clearly 

 [ marked, the short and wide gullet being 

 ! hardly distinguishable from the stomach. 

 The pancreas, for the most part, retains its 

 primitive condition of separate csecal ap- 

 pendages to the duodenum. The heart con- 

 Isists essentially of one auricle, and one ven- 

 tricle, receiving the venous blood, and pro- 

 | pelling it to the gills j whence the circulation 

 | is continued over the entire body in vessels 

 I only, which are aided by the contraction of 

 the surrounding muscular fibres. The blood 

 of fishes is cold ; its tem|>erature being rarely 

 elevated above that of the surrounding me- 

 dium." 



" All writers on animal mechanics," ob- 

 serves the able Professor just quoted, and 

 to whom we are indebted for the following 

 detached extracts, " have shown how ad- 

 mirably the whole form of the fish is adapted 

 to the element in which it lives and moves : 

 the viscera are packed in a small compass, 

 in a cavity brought forwards close to the 

 head, and whilst the consequent abrogation 

 of the neck gives the advantage of a more 

 fixed and resisting connection of the head to 

 the trunk, a greater proportion of the trunk 

 behind is left free for the development and 

 allocation of the muscular masses which are 

 to move the tail. In the caudal, which is 

 usually the longest, portion of the trunk, 

 transverse processes cease to be developed, 

 whilst the dermal and intercalary spines 

 shoot out from the middle line above and | 

 below, and give the vertically extended, I 

 compressed form, most efficient for the la- ' 

 teral strokes, by the rapid alternation of ] 

 which the fish is propelled forwards in the 

 diagonal, between the direction of those 

 forces." " You may be reminded that nil 

 the vertebrae of the trunk are distinct from 

 one another at one stage of the quadruped's 

 development, as in the fish throughout life ; 

 and you might suppose that the absence of 

 that development and confluence of certain 

 vertebrae near the tail, to form a sacrum, 

 was a mark of inferiority in fishes. But 

 note what a hindrance such a fettering of j 

 the movements of the caudal vertebra; would I 

 be to creatures which progress by alternate j 

 vigorous inflections of a muscular tail. A 

 sacrum is a consolidation of a greater or less 

 proportion of the vertebral axis of the body, 

 for the transference of more or less of the 

 weight of the body upon limbs organized for 

 its support on dry land ; such a modification 

 would have been useless to the fish, and not 

 only useless, but a hindrance and a defect. 



" The pectoral fins, those curtailed proto- 

 types of the fore-limbs of other Vertebrata, 

 with the last segment, or hand, alone pro- 

 jecting freely from the trunk, and swathed 

 in a common undivided tegumentary sheath, 

 present a condition analogous to that of the 

 embryo buds of the homologous members in | 

 the higher Vertebrata. But what would i 



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