MYOLOGY OF FISHES. 637 



which are in this case of secondary importance as locomotive instru- 

 ments, exhibit a very rudimentary condition, and are but feeble agents 

 in progression. 



(1732.) The posterior extremities, or ventral fins, are even less effi- 

 cient than the pectoral in this respect, and their position is found to 

 vary remarkably in different orders. In the Perch, these organs are, 

 as we have seen, attached to the bony framework of the shoulders. 

 In the Carp tribe (Cyprinidae) they are removed far back towards the 

 commencement of the tail, and the bones supporting them are merely 

 imbedded in the muscles of the abdomen. In the Cod (Gadidae) the 

 legs are absolutely in front of the arms, being suspended under the 

 throat ; and in the Anguilliform fishes, the Eel for instance, the ventral 

 extremities are altogether wanting. 



(1733.) Such being the imperfect development of the usual locomotive 

 organs, we are quite prepared to expect a corresponding modification in 

 the disposition and efficiency of different parts of the muscular system. 

 When we compare the muscles of a fish with those of any of the higher 

 Vertebrata, the contrast is indeed very striking. 



Fig. 314. 



Myology of the Perch. (After Cuvier.) 



(1734.) Delicate muscles (fig. 314) are provided for the erection or 

 depression of the different rays sustaining the dorsal and ventral fins, 

 and thus the fins themselves are expanded or folded up at pleasure. 

 Similar fasciculi spread out or approximate the rays of the tail, in- 

 creasing or contracting at will the extent of surface presented by that 

 organ. The muscles of the pectoral and ventral limbs are small in 

 proportion to the feebleness of these extremities ; the muscles of the 

 trunk alone constitute the great bulk of the body, and form the efficient 

 agents in progression. 



(1735.) These great lateral masses commence at the back of the 



