THE SHOEES OF BEITAIN, C9 



distingiiisLable ; such as those of the Eel : to procure 

 these for microscopical examination, " take a piece of 

 the skin of the Eel that grows on the side, and while 

 it is moist spread it on a piece of glass, that it ma y 

 dry very smooth ; when thus dried, the surface will 

 appear all over dimpled or pitted by the scales, wliich 

 lie under a sort of cuticle, or thin skin : this skin 

 may be raised with the sharp point of a penknife, 

 together with the scales, which will then easily slip 

 out, and thus you may procure as many as you 

 please." * 



The limbs of fishes differ greatly in appearance 

 from those of terrestrial animals ; consisting, as to 

 the portion external to the body, of slender spines, 

 sometimes cartilaginous and jointed, at others bony 

 and simple, united by means of a thin membrane 

 stretched from one to the other. Generally there 

 are two pairs on the under part of the body, which 

 are called the pectoral and the ventral fins, and 

 represent respectively the fore and hind legs of 

 quadrupeds, or the wings and feet of a bird. Besides 

 these, there are one or more perpendicular fins along 

 the back, called the dorsal, and one below the body, 

 near the tail, called the anal ; but the main instru- 

 ment of motion is the broad, perpendicular fin, which 

 terminates the body, often called the tail, but, more 

 con-ectly, the caudal or tail fin. To rightly under- 

 stand the motions of a fish, we must bear in mind 

 that it is immersed in a fluid which is of little less 

 specific gravity than its own body ; but in order to 

 regulate its own weight, it is in general provided with 



* Martin's Microcrapljia Nova, p. 29. 



