80 'INTERNAL ORGANS. 



other ; these are brought into use principally at 

 the time of moulting. In the legs and prolegs 

 the walls are coated with short muscular ribands, 

 uniting the hinder portions of contiguous joints, 

 a miniature of the longitudinal muscles of the 

 body ; but besides these, a tendinous cord runs 

 through the middle of the true legs, attached at 

 one extremity to the claw, and connected through- 

 out with muscles running obliquely to the walls 

 of the leg. 



The digestive system consists of an alimentary 

 canal with anterior and posterior appendages ; 

 the canal is a simple, cylindrical, muscular tube 

 extending in a straight line from one end of the 

 body to the other, enlarging in certain places and 

 contracting in others, so that it may be divided 

 very naturally into an oesophagus, a stomach, 

 and an intestine. The oesophagus is a simple 

 slender tube, enlarging to a sort of crop near the 

 middle of the thoracic joints ; the stomach is a 

 much larger tube, of uniform size, extending 

 nearly to the extremity of the body and covered 

 with muscular threads, which run transversely, 

 diagonally, and longitudinally ; at about the sev- 

 enth abdominal segment this tube suddenly con- 

 tracts, and opens by a slender orifice to the intes- 

 tine, the anterior half of which is tightly wrapped 

 in strong muscular fibre, running in various direc- 

 tions, so as to mould the interior walls into prom- 



