INTRODUCTION. 



visible. It arises from the upper part of the 

 head, at b c, and the bones of the shoulders, and 

 is inserted into the sides of the bone of the tail. 

 It is separated above from its corresponding 

 muscle on the opposite side, by the spine and its 

 epiphysis, by the deep muscles of the interspinal 

 bones, and by the ribs which surround the ab- 

 dominal cavity ; beneath it widens to admit the 

 lower fins and the muscles which belong to them. 

 The structure of this great muscle is complicated. 

 It is transversely composed of slips held together 

 by a tendinous expanse, and which generally 

 equal the vertebrae in number. The layers or 

 plates are best seen when the fish is boiled, and 

 the cartilaginous substance has been dissolved. 

 Longitudinally it is divided into three bands. 

 In the centre band a slight furrow may be 

 observed, d e, in which are placed the mucous 

 glands. 



The late Baron Cuvier assumes the common 

 perch, among fishes, as the form in which the 

 greatest general perfection is exhibited (see 

 Common Perch, Plate XXXV.); and being a 

 species familiarly known to almost every one, will 

 serve better than any other to convey an idea 

 of this class of beings; and the accompanying 

 Plate (XXXII. of the Skeleton of the Common 

 Perch), exhibits the bony structure in osseous 



