THE FRESH-WATER MUSSEL. 91 



end will point toward you and the small end away from 

 you. Then, if you slip the edge of a thin-bladed knife 

 in between the shells at the small end (keeping the 

 knife close to the shell) and drawing it carefully tow- 

 ard you, you will cut the two straps, or muscles, of the 

 left side, and then you can lift up the left half of the 

 shell, and you can also see where the straps have been 

 fastened to the shell (Fig. 91). The muscle on the 

 large or front end is called the anterior adductor, 

 and the one near the small back end the posterior 

 adductor. They are called adductors, because they 

 bring to and keep together the sides of the shell ; the 

 word adductor comes from the Latin — ad y to ; and duco, 

 I lead. So the adductor muscles lead, or bring to, the 

 mussel's shells. After you lift the shell, you will see 

 a mass of slimy-looking substance ; but this is not all. 

 If you take hold of the yellowish edge toward your left 

 hand, you will find that it lifts up as you lifted up the 

 shell (Fig. 91). This edge seems to be the border, or 

 trimming, of our little friend's cloak, which is shaped 

 quite like the shell ; in fact, it lines the shell with its 

 two halves. These halves are joined together on the 

 upper or dorsal edge, and they are also united for a little 

 distance on the ventral, or lower edge — at the back, or 

 posterior end, so that you might call these two linings 

 of the shell the mussel's blankets in which he lies ; but 



