ably large; but the muscles have no tendinous chords, their insertions being always fleshy. There are, however, semi-transparent pearly tendons placed between the plates of muscles, which give origin to a series of short muscular fibres, passing nearly at right angles between the surfaces of the adjoining plates.
The progressive motion of fishes, our, author says, is chiefly performed by the flexions of the trunk and tail; the pairs of fins, which some have considered as analogous to feet, being only employed for the purposes of turning, stopping, altering the position of the fish towards the horizon, and keeping the hack upwards. The single fins appear to prevent the rolling of the body whilst the tail is employed to impel it forwards. Each of the fins, which are in pairs, is capable of four motions, viz. of flexion and extension, like oars, and of expanding the rays, and closing them.
Mr. Carlisle now (taking the Cod as a standard of comparison,) describes particularly the mode in which the various motions here spoken of are performed, and then relates some experiments made to determine the effect of the fins on the motions of fishes. For this purpose a number of dace, equal in size, were put into a large vessel of water, and the pectoral fins of one of them being out off, it was replaced with the others. The result was, that the progressive motion of the fish was not at all impeded; but its head inclined downwards; and when it attempted to ascend, the effort was attended with difficulty.
From another fish, both the pectoral and abdominal fins were taken. The fish remained at the bottom of the vessel, and could not be made to ascend. Its progressive motion was not perceptibly more slow; but when the tail acted, the body showed a tendency to roll, and the single fins were widely expanded, as if to counteract this effect.
From a third fish the single fins were removed. This produced an evident tendency to turn round, and the pectoral fins were kept constantly extended, to obviate that motion.
From a fourth fish all the fins were removed. Its back was kept in a vertical position, whilst at rest, by the expansion of the tail; but it rolled half round at every attempt to move.
From a fifth fish the tail was cut off as close to the body as possible. The progressive motion of the fish was considerably impeded, and the flexions of the spine were much increased; but neither the pectoral nor the abdominal fins seemed to be more actively employed.
From a sixth fish all the fins and the tail were removed. It remained without motion, floating near the surface of the water, with its belly upward.
The above experiments were repeated on the roach, the gudgeon, and the minnow, with similar results.
Mr. Carlisle now observes, that the muscles of fishes differ very materially in their structure from those of other animals; that they are apparently more homogeneous; that their fibres are not so much fasciculated, but run more parallel to each other, and are always
