The Internal Anatomy of Spiders 



cavity be closed as tightlyas possible bythe pressing togetherof the 

 epipharynx and the hypopharynx there will still remain an open 

 way for the passage of the last drop of fluid pressed from the prey. 

 At the upper end of the pharynx near the entrance to the 

 oesophagus there is a straining apparatus consisting of hairs which 

 prevent the entrance of solid food into the oesophagus. 



Several pairs of muscles extend from the walls of the pharynx 

 to the body-wall; one of these, the retractor of the pharynx, 



is attached to the 

 upper end of the 

 pharynx and is 

 sometimes very 

 large. 



Within the ros- 

 trum there is an 

 unpaired gland, the 

 pharyngeal gland, 

 which opens into 

 d - the pharynx near 

 the beginningof the 

 oesophagus. 



The (Esopha- 

 gus. — This is that 

 part of the fore- 

 intestine that con- 

 nects the pharynx 

 with the sucking 

 stomach; it extends 

 in a more or less 

 nearly horizontal 

 direction and con- 

 sequently nearly at right angles to the pharynx. It is tubular 

 in form; and the intima of its dorsal and lateral walls is thick 

 and strong, forming an inverted gutter-like sclerite, which is 

 transversely striated. The epithelium of the oesophagus is 

 greatly reduced. The hind portion of the oesophagus is sur- 

 rounded by the central nervous system; the course of this part 

 of it is indicated in Fig. 143 by dotted lines. 



The sucking stomach— -The sucking stomach is an enlarged 

 portion of the fore-intestine, whose function is indicated by its 



Fig. 161. CROSS-SECTION OF THE SUCKING STOMACH 



AND ADJACENT PARTS 



a, dorsal plate b, lateral plate c, ventral plate d, endosternite 



ee, sphincter muscles (after Vogt et Yung) 



154 



