Circulation of Helix pomatia. 5 



and supplies the posterior portion of the foot with blood. The 

 aorta, after giving off these trunks, runs straight forward to the 

 inferior oesophageal ganglion (fig. \p) without giving off any 

 large branches, having the crop on its superior surface, the 

 retractor muscle of the head below, with the visceral nerve 

 closely adhering to its left side. After perforating the inferior 

 oesophageal ganglion, it splits into two branches, the first and 

 smaller of which proceeds into the buccal mass. A small branch 

 comes up on each side of the infra-oesophageal mass, adhering 

 closely to the nerve-collar, supplies the tentacles (fig. 1 o), 

 parts about the head, the whip and sheath of the penis, and 

 anterior sides of the body. The second and larger bends sharply 

 back round the inferior surface of the ganglion, and runs along 

 the surface of the foot between the bundles of retractor muscles 

 (fig. \g), and gives off branches throughout its course to all 

 those parts not supplied by the posterior pedal*. The aorta 

 therefore does not, as Milne-Edwards and others maintain, 

 when it reaches the head, terminate in a large sinus which 

 surrounds the collar, but can with ease be traced into the sub- 

 stance of the foot, where it ends in a capillary system. 



Two large veins collect the venous blood from the capillaries 

 of the body, foot, &c., and unite to form a large sinus, which 

 runs along the side of the rectum ; and from it the blood passes 

 to the pulmonary capillaries. The most superficial of these veins 

 commences at the posterior part of that portion of the liver 

 which is contained in the spire of the shell, runs along the 

 thickened rim of the mantle, receives in its course numerous 

 large twigs which come up from the surface of the liver, and 

 forms a junction with the second vein at the posterior extremity 

 of the pulmonary chamber. The second vein collects the blood 

 from the foot, the mantle, the skin covering the head, the ante- 

 rior and lower surface of the liver, and forms a considerable 

 sinus, which runs along the posterior border of the kidney and 

 finally joins the first superior vein, to form a sinus at the point 

 where the rectum leaves the visceral covering. A third and 

 much smaller trunk runs along the wall of the intestine, receiv- 

 ing the blood from its rich plexus of capillaries, and, getting 

 larger as it proceeds towards the rectum, enters the venous sinus 

 close by the last two veins. The large sinus formed by the 

 junction of these three veins runs along the outer border of the 

 rectum (fig. 2 c), covered over by the mantle which is common 

 to both, and when it reaches the pulmonary orifice it closes over 

 its inferior surface and runs across in the thickened border of the 

 mantle, giving off twigs to the whole of the pulmonary chamber. 



* For Cuvier's brief account of the vascular system of Helix, see ' Memoires 

 des Mollusques,' Paris, 1817; or Ann. du Museum, 1806, p. 159. 



