Pleura (Gr. πλευρά, the side, also a rib). A membrane covering the lung, and lining the chest.
Pleurisy. An inflammation affecting the pleura.
Pneumogastric (Gr. πνεύμων, the lungs, and γαστήρ, 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. πρέσβυς, old, and ὤψ, 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.