DIGESTIVE SYSTEM OF SPIDEE. 



371 



vessels forms the only distinction between its ventricular and intestinal 

 divisions. Five delicate caeca are derived from each side of the ven- 

 tricular portion, and plunge into the centre of a fatty substance in 

 which the alimentary canal is imbedded. In Spiders, likewise, caeca 

 are appended to the commencement 

 of the digestive apparatus ; and a 

 slight enlargement (fig. 186, b) may 

 be said to represent the stomach, 

 from which a slender intestine (g) 

 is continued to the anus. As in 

 the Scorpion, a large quantity of 

 fat (h) surrounds the nutrient 

 organs and fills up a great propor- 

 tion of the cavity of the abdomen. 

 Like the fat-mass of the larvae of 

 insects, this substance must, no 

 doubt, be regarded as a reservoir of 

 nutriment ; and when the habits 

 of these animals are considered, the 

 precarious supply of food, and the 

 frequent necessity for long-pro- 

 tracted fasts when a scarcity of 

 insects deprives them of their ac- 

 customed prey, such a provision is 

 evidently essential to their preser- 

 vation. 



(960.) One peculiarity connected 

 with the arrangement of the chy- 

 lopoietic viscera of the Spider is 

 the manner in which the biliary 

 organs terminate in the intestine ; 

 for instead of entering in the usual position, namely close to the termi- 

 nation of the stomach, they seem to pour their secretion into the rectum, 

 immediately in the vicinity of the anus. At this point, a kind of 

 sacculus (figs. 186 & 188,/) joins the intestine, into which the branched 

 tubes (fig. 188, o o, & fig. 186, s) empty themselves. This circumstance 

 has long been a subject of interesting inquiry to the comparative physio- 

 logist. If the fluid secreted by these tubes be really bile, in what 

 manner does it accomplish those purposes usually supposed to be effected 

 by the biliary secretion ? It would seem to be, in this case, merely an 

 excrementitious production. Are the caeca appended to the stomach 

 biliary organs ? If so, the apparatus in question may be of a totally 

 distinct character, and its product only furnished to be expelled from 

 the system. In conformity with the last supposition, many anato- 

 mists have been induced to regard these vessels as being analogous to 



Digestive system of the Common Spider : 

 c, poison-fang; oo, the jaws, with their ap- 

 pended poison-glands; a a a, caecal append- 

 ages to d, the commencement of the alimen- 

 tary canal, with which the muscle (e) is con- 

 nected ; 6, stomachal dilatation ; g, intestine ' 

 h h, accumulation of fat ; f, sacculus receiving 

 the terminations of the secreting-tubes (). 



