GENERAL ANATOMY OF THE SQOD. 341 



found, running backwards and downwards around the 

 body into the mantle, where it divides into an anterior 

 and a posterior branch, which pass into the muscular layer 

 of the mantle. These bodies (Fig. 177, ic) are made up 

 of an artery and a vein, united in a common fold of me- 

 sentery, the lateral mantle artery and the posterior vena 

 cava. In an alcoholic specimen the vein is usually gi-eatly 

 distended by coagulated blood. 



s. Posterior to these arteries is the large visceral sac 

 (Fig. 177, x), reaching to the posterior end of the body, 

 and covered by a delicate, transparent mesenteric mem- 

 brane, which is reflected out along the ventral mantle 

 artery and along the back, into the inner face of the 

 mantle. 



t. Make a drawing, showing as many of these parts as 

 possible. 



III. The Circulatory and Renal Organs. 



With a pair of fine-pointed scissoi-s cut through the thin 

 membrane of the two renal organs, by a transverse incision 

 just behind their external openings ; and placing the speci- 

 men under water, pull ofi", with a fine pair of forceps, the 

 wall of the renal organs, thus exposing their cavities 

 (Fig. 178, g). With a stream of water, or a fine bmsh, 

 gently wash away the fine white granular substance, which, 

 in an alcoholic specimen, usually fills the cavity, and notice 

 the intestine (Fig. 178, /i), which lies between the two 

 chambers. 



a. On each side of this, notice a large, white, glandular 

 body, which almost entirely fills the cavitj^ of the renal 

 organ ; this is the glandular portion of the anterior vena 

 cava (Fig. 178, i). 



The anterior ends of the venae cavse of the two sides of 

 the body bend down under the intestine, where they unite 

 to form one median trunk, which wiU be noticed later. 



