bones of the fingers and toes.

Pharynx (Gr. pharmgxi, the throat). The cavity between the back of the
mouth and the gullet.

Physiology (Gr. physis, nature, and logos, a discourse). The science of
the functions of living, organized beings.

Pia Mater (Lat.). Literally, the tender mother; the innermost of the three
coverings of the brain. It is thin and delicate; hence the name.

Pinna (Lat. a feather or wing). External cartilaginous flap of the ear.

Plasma (Gr. plasso, to mould). Anything formed or moulded. The liquid part
of the blood.

Pleura (Gr. pleura, the side, also a rib). A membrane covering the lung,
and lining the chest.

Pleurisy. An inflammation affecting the pleura. Pneumogastric (Gr.
pneymon, the lungs, and gaster, the stomach). The chief nerve of
respiration; also called the _vagus_, or wandering nerve.

Pneumonia. An inflammation affecting the air cells of the lungs.

Poison (Fr. _poison_). Any substance, which, when applied externally, or
taken into the stomach or the blood, works such a change in the animal
economy as to produce disease or death.

Pons Varolii. Bridge of Varolius. The white fibers which form a _bridge_
connecting the different parts of the brain, first described by
_Varolius_.

Popliteal (Lat. _poples_, _poplitis_, the ham, the back part of the knee).
The space _behind the knee joint_ is called the _popliteal_ space.

Portal Vein (Lat. _porta_, a gate). The venous trunk formed by the veins
coming from the intestines. It carries the blood to the liver.

Presbyopia (Gr. presbus, old, and ops, the eye). A defect of the
accommodation of the eye, caused by the hardening of the crystalline lens;
the "far sight" of adults and aged persons.

Process (Lat. _procedo_, _processus_, to proceed, to go forth). Any
projection from a surface; also, a method of performance; a procedure.

Pronation (Lat. _pronus_, inclined forwards). The turning of the hand with
the palm downwards.

Pronator. The group of muscles which turn the hand palm downwards.

Proteids (Gr. protos, first, and eidos, form). A general term for the
albuminoid constitutents of the body.

Protoplasm (Gr. pro#x1FF6;tos, first, and plasso, to form). A
_first-formed_ organized substance; primitive organic cell matter.

Pterygoid (Gr. pteron, a wing, and eidos, form, resemblance). Wing-like.

Ptomaine (Gr. ptoma, a dead body). One of a class of animal bases or
alkaloids formed in the putrefaction of various kinds