For this purpose the shell should be prised open by means of some flattened but blunt implement, such as the handle of a scalpel, and then, after inserting a piece of cork to keep the valves apart, gently remove the mantle lobe from the valve which is held uppermost with the same implement, being careful to separate it from the shell without doing any damage to the soft structures. Separating the mantle from the shell in this way we meet with one or more hard masses of muscle that are joined very firmly to the latter. These are the adductor muscles that pass directly from valve to valve, and on cutting them through close to the uppermost valve, the latter can be raised so as to expose the body of the animal, mostly hidden by the overlying mantle lobe. Before raising the upper mantle lobe we observe the heart, on the dorsal margin of the body, near the hinge of the shell, situated in a transparent cavity (the _pericardium_) containing a colourless fluid. It consists of at least two cavities--a thick-walled ventricle and a thin-walled auricle, and its slow pulsations may be watched with or without the use of a hand lens. On opening the pericardium the heart is still better seen, and if we carefully cut into the thick-walled ventricle we find a tube running completely through its cavity. This is the _rectum_--the last part of the digestive tube, that commences at the mouth, and terminates in a cavity at the posterior end communicating with the exhalent siphon. After noting the nature and position of the one or two adductor muscles previously cut through, we turn the upper mantle lobe upwards, laying it back over the hinge of the shell, cutting it through at the bases of the siphons if we find it is united with the opposite lobe at those points; or, if not united, we observe two points at which the lobes touch each other in order to form the siphonal openings. Several organs are now exposed to view. The lower mantle lobe is seen in close contact with the valve below it, and if we touch its edge we shall probably observe that it is retracted slightly by the contraction of its own muscular fibres. The tip of the foot is also seen projecting towards the anterior end, its base being hidden between the two sets of plate-like gills that extend along the length of the body. On touching the tip of the foot we find it retract by the contraction of the muscular fibres of which it is composed, aided, perhaps, by the action of one or more _retractor pedis muscles_ with which it is supplied. On raising the upper gill-plates we may observe the dark colour of the digestive gland (liver) at the base of the foot, and also see two or more _tentacles_ or _labial palpi_ on the anterior side of the same.