314 FISHES. 



front. In the trout, there are three solutions of continuity nearly 

 equally well marked, the two ordinary ones and a middle one. 



In fishes with depressed bodies, the superior and inferior bands are 

 horizontal and parallel to each other ; in these the inferior, still more 

 obviously, performs the functions of the abdominal muscles. 



The great lateral muscles terminate behind by an aponeurosis, 

 which is inserted by tendinous slips in the base of the rays of the 

 caudal, which it laterally supports. Even some of the »mall muscles 

 belonging to this fin are inserted into this aponeurosis; it also 

 conceals its deep seated muscles. Tlie superior and inferior bands 

 are inserted more particularly in the extreme rays, and seem to 

 concur in separating them from the others, and dilating the caudal. 



The use of the great lateral muscles is obvious : each of them 

 bends from its side the whole or part of the body of the fish, and 

 consequently all impart to it those alternating motions of flexion and 

 extension which carry the fish forwards ; for it is by the strokes 

 which the tail and to a certain extent the whole body, give laterally 

 to the Avater, that the fish moves in this direction. The anterior 

 inferior portion which goes to the symphysis of the humeral bones, 

 and thence to the body of the os hyoides, representing the sterno, and 

 cleido-hyoideans, concurs with the genio-hyoidean, which we shall 

 notice in the sequel, in bringing down the lower jaw, and conse- 

 quently in opening the mouth. As the head has no muscles proper 

 to it in osseous fishes, it is to the great lateral muscles, that it owes 

 the slight movements which it executes. This, however, is not the 

 case in the chondropterygians in which the hea.d is furnished with 

 muscles proper to itself. 



The Thin, Superior, and Inferior Muscles of the Trunk. 



In the interval of the two great lateral muscles, either at the b^ack, 

 or more frequently also at the belly, there are two thin muscles, 

 which commonly are only interrupted by the dorsal and anal fins, to 

 the anterior and posterior bases of which they are attached ; they 

 move these fins, but they also serve to curve the trunk, either 

 upwards or downwards, whenever the disposition of the vertebrae 

 renders such movements possible. 



In the perch, whose dorsals commence at the nucha, there is but 

 one superior pair of these muscles, and they can only be seen between 

 the second dorsal and the caudal (No. 7); but inferiorly, there are 

 two pairs, one (No. 6) proceeding from the posterior part of the 

 pelvis to the anal, embracing the anus ; the other (No. 8) extends from 

 the anal to the caudal, and corresponds with the dorsal portion (No. 7). 



In fishes Avhich have but one dorsal more or less short, as in the 

 cyprins, there are two pairs on the back, and when there are two 

 dorsals separated from each other, as in trouts, there are three pairs ; 

 but when there are two or three dorsals in contact, and occupying a 

 large portion of the back, as in the cods, the muscles of that side are 

 considerably reduced in size. 



The same variations obtain with regard to those of the belly. 



In the abdominal fishes, whose ventrals are remote from the 

 pectorals, there are three well marked pairs ; one proceeding from the 



