as Elementary Manual of Zoology. 
posterior end of the digestive tract. Above this is the greenish mass of 
the liver, which exteuds up to the top of the shell. Below notice the large 
(columella) muscle by the contraction of which the animal draws itself 
back into its shell. 
Pin the specimen, ventral surface downwards, on to the weighted bark. 
Open up the pulmonary chamber with scissors and dissect off the mem- 
brane with which it is covered. Notice the numerous vessels containing 
colourless blood, which ramify through the walls of the breathing 
chamber. See the large pulmonary vein with which the branching veins 
unite. The pulmonary vein conveys the blood back to the heart after 
it has been oxidized in the pulmonary chamber. 
Slit open the pericardial chamber and observe the heart which it 
contains. The heart consists of a thin-walled auricle, which receives the 
blood from the pulmonary chamber, and a thick-walled ventricle, which 
pumps the blood to all parts of the body, whence it finds its way back to 
the pulmonary chamber. The kidney is in communication with the peri- 
cardial chamber ; its duct (the ureter) passes down to open close to the 
anus. 
Find the anus and push a piece of match or grass up into the diges- 
tive tract, which is thin walled and sometimes rather difficult to see 
through the investing membranes. Then with scissors carefully dissect 
away the membrane around so as to clear the digestive tract. Trace it 
through its convolutions in the mass of the liver and dissect it out 
throughout its entire Jength until it terminates in the mouth in front. 
In doing this take care not to cut through the fibrous collar by which 
the digestive traet is encircled just behind the mouth, Notice that the 
digestive tract consists of the following parts :— 
(1) A large mouth: in front, which contains the toothed tongue 
(odontophore) by means of which the snail gnaws the 
leaves on which it feeds. 
(2) A narrow gullet (cesophagus), which connects the mouth with 
the expanded crop behind. It passes through the thick 
fibrous collar, which contains the chief nerve centres. 
(3) A thin-walled, expanded crop, to which a quantity of white 
glandular matter (salivary gland) is closely attached. The 
salivary gland pours its secretion through slender ducts 
which open into the mouth. 
(4) A thick-walled, expanded loop or stomach, which receives the 
ducts from the liver. 
(5) A narrow, thin-walled, winding intestine, which traverses the 
liver, and ultimately passes into the rectum, by which it 
is connected with the anus, 
On the right-hand side of the digestive tract the complicated repro- 
ductive organs will now be exposed, Dissect them out by snipping away 
