130 



FIRST LESSONS IN ZOOLOGY. 



wide, we see that the jaws are armed with numerous fine 

 teeth, as are also the bony projections on the sides and roof 

 of the mouth; the teeth are seen to be sharp, conical, and 

 curved backwards, so that the jaws can retain a slippery fish 

 in their grasp. 



The shape and arrangement of the scales should also be 

 noted, as well as the "lateral line" (Figs. 137, ms; 139, 7,). 



m.a 



eft 



FIG. 137. The minnow and its internal structure. A: , nose; r/c, pill cover; /, 

 pectoral or arm fin; J/, leg-fin or ventrals; rlf, dorsal fin;Ct/, anal fin; </, caudal 

 fin; (s, mucous scales of the lateral line. B: ?i, nose-pit; e, eye-nerve; ea, 

 ear-nerve leading from the brain; j/, gills; /i, heart; f, (esophagus; s, stomach; 

 A-. kidney; v. vent; da, dorsal artery; , air-bladder; l>, backbone; nv, nerve 

 cord or spinal cord. 



A well-prepared skeleton of a f erch (Fig. 138) or cod 

 should then be studied. The chief point of interest is the 

 spinal or vertebral column, which consists of vertebrae. 



From each vertebra arises a dorsal or spinous process (g), 

 and a similar process below called the "haemal spine" (e). 

 These form the support of the dorsal, anal, and caudal fins. 

 The spinal cord or nerve passes from the brain through the 



