Sebaceous (Lat. sebum, fat). Resembling fat; the name of the oily secretion by which the skin is kept flexible and soft.
Secretion (Lat. secerno, secretum, to separate). The process of separating from the blood some essential, important fluid; which fluid is also called a secretion.
Semicircular Canals. Three canals in the internal ear.
Sensation. The perception of an external impression by the nervous system.
Serum. The clear, watery fluid which separates from the clot of the blood.
Spasm (Gr. σπασμός, convulsion). A sudden, violent, and involuntary contraction of one or more muscles.
Special Sense. A sense by which we receive particular sensations, such as those of sight, hearing, taste, and smell.
Sputum, pi. Sputa (Lat. spuo, sputum, to spit). The matter which is coughed up from the air passages.
Stapes. Literally, a stirrup; one of the small bones of the middle ear.
Stimulant (Lat. stimulo, to prick or goad on). An agent which causes an increase of vital activity in the body or in any of its parts.