HELIX — CIRCULATORY SYSTEM. 
loo 
the renal organ ; the hnal tract or rectum runs along the right margin 
of the pulmonary cavity, beneath the ureter, and terminates at the 
anus upon the posterior side of the respiratory orifice. 
The Circulatory or Vascular system has for its centre and motor 
the heart, which in Helix aspersa is, as in the Gastropoda generally, 
divided into two chambers of approximately equal size, the auricle 
and the ventricle ; the auricle has delicate walls and receives the 
aerated blood by the pulmonary vein from the respiratory plexus and 
passes it forward to the pyriform muscular ventricle, regurgitation 
being prevented by a valvular arrangement at the junction of the 
vessels. The heart is confined within a 
thin-w'alled oval cavity or pericardium, 
placed on the left posterior side of the roof 
of the matitle chamber and in close and 
actual connection with the renal organ by 
the reno-pericardial funnel. The heart being 
exclusively occupied in propelling the blood 
through the system, is termed a systemic 
heart. The ventricle transmits the oxy- 
genated blood received from the auricle by 
a single trunk or aorta, which bifurcates on entering the body cavity, 
dividing into an anterior and a posterior trunk ; the anterior runs 
parallel with the sacculated oviduct and along the right side of the 
crop, passing beneath the intestinal tract and the spermatheca to the 
right side of the body, giving branches to the salivary glands and the 
anterior part of the foot ; it then passes through the nerve collar 
between the pedal and aggregated visceral ganglia and is distributed 
to the buccal mass and neighbouring parts. 
The posterior aorta is at first associated with the intestinal tract 
and maiidy supiilies the alimentary system and its dependent organs, 
running (j^uite to the summit of the spire, contributing the blood 
supply to both lobes of the liver, the gonads, etc., on its course. 
These distinctly defined arterial vessels break up into more minute 
vessels or empty themselves by funnel-shaped openings into irregular 
blood spaces or lacunte amongst the connective tissue, which has hence 
been termed lacunar tissue (see figs. 291 and 296). These smaller 
blood spaces eventually unite with the large visceral sinus, which 
runs from the top of the spire within the thickened upper edge of the 
spirally-coiled visceral sac, or with one of the two large lateral sinuses 
F(g. 318. — Heart of Helix 
aspersay showing the connection 
of auricle and venti4cle and in- 
dication of walls of pericardium 
(highly magnified). 
a. auricle ; v, ventricle. 
