THE TRUE FISHES. 155 
and over three hundred and fifty in cartilaginous ones, 
that in the former are hollow upon each side, the inclosure 
so formed containing a glutinous substance. The verte- 
bre are all connected at their edges by ligaments, that 
allow more or less lateral motion. To the central or ab- 
dominal ‘portion of the backbone the ribs are attached, 
their lower ends hanging free in the muscles. The head 
Fic. 193.—Skeleton of the perch (Perca fluviatilis), Shows the jointed na- 
ture of the vertebral column, and the facilities afforded for latera] motion, 
particularly in the tail (d), dorsal (e,/), ventral (6, c), and pectoral (2) 
fins, which are principally engaged in swimming. 
is made up of a complicated arrangement of bones ; the 
jaws armed with many rows of teeth, in some cases being 
movable. The limbs or fins are formed of bony or carti- 
laginous rays ; those in pairs corresponding to the limbs 
of man. Thus, the pectoral fins (Fig. 193, 2) correspond 
to the arms. A pectoral arch, scapula, clavicle, and cora- 
coid bones are found, and generally the ulna, radius, and 
carpus. The lower portion of the fish is termed ventral, 
and the ventral fins (Fig. 193, 4) that are attached to 
the pelvic arch represent the hind-limbs, though the bones 
of these limbs are not present. The single fin (Fig. 
193, ¢) is a lower middle fin, that is supported by inter- 
spinous bones, that in turn are connected with the verte- 
bra by ligaments. The tail or caudal fin (Fig. 193, 2) 
is formed of a number of spreading rays, and is of two 
