2 Mr. Carlisle’s Lecture on the Arrangement 
instruments employed for their progressive motion, give them 
a character peculiarly distinct from the rest of the creation. 
The frame-work of bones or cartilages, called the Skeleton, 
is simple ; the limbs are not formed for complicated motions, 
and the proportion of muscular flesh is remarkably large. 
The muscles of fishes have no tendinous chords, their in- 
sertions 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. Lewenhoeck* appears to have overlooked 
these tendons, and the numerous vessels, which he describes 
in the interstices of the muscular flakes, I have not been able 
to discern. 
The motion of a round shaped fish, independent of its fins,, 
is simple ; and as it is chiefly effected by the lateral flexure of 
the spine and tail, upon which the great mass of its muscular 
flesh is employed, whilst the fins are moved by small 
muscles, and those, from their position, comparatively but of 
little power, I shall only describe in detail the arrangement 
and application of those masses, which constitute the principal 
moving organs. 
For this purpose a well known fish, the cod,-f has been 
selected as a standard of comparison for the muscles of other 
fishes, there being a conspicuous resemblance among them 
all. 
The pairs of fins have been considered as analogous to 
feet, but they are only employed for the purposes of turning, 
stopping, altering the position of the fish towards the horizon, 
* Phil. Trans. Vol. XXXI. p. 190. t Gadus Morhua of LiNN^r's, 
