OBSTETRICS.--The branch of medicine which deals with the treatment and care of women during pregnancy and child-birth. OVARY.--The organ which contains the egg-cells or ova. OVIDUCTS.--Two tubes, each of which leads from the neighborhood of one of the ovaries; both terminate in the uterus. OVUM.--An egg: the cell contributed by the mother to her offspring. OXYGEN.--One of the chemical elements. PATHOLOGY.--The branch of medicine which deals with the altered structure and activity of diseased organs. PEPSIN.--A ferment found in the digestive juice secreted by the stomach. PELVIC FLOOR.--The muscles, ligaments, and other tissues which form the bottom of the basin inclosed between the hips. PELVIS.--The bony ring formed chiefly by the hip bones. Posteriorly the ring is completed by the sacrum. PERINEUM.--The region extending backward from the outlet of the vagina to the rectum; it is the most essential part of the pelvic floor. PHYSIOLOGY.--Scientific knowledge of the manner in which the various parts of the body perform their duties. PIGMENT.--Any coloring matter. PLACENTA.--The organ through which the communication between the mother and the offspring is established. One of its surfaces is attached to the wall of the uterus; at about the middle point of the other surface the umbilical cord takes its origin. PRENATAL.--Pertaining to the period before birth. PROTEIN.--A food-stuff which is distinguished by the fact that it contains nitrogen and is a tissue builder. PROTOPLASM.--The living substance in the cells which compose our bodies. PUBERTY.--Sexual maturity in human beings. PUBIC BONES.--The part of the pelvis which forms an arch in front of the bladder. PUERPERIUM.--The same as the lying-in period. RETINA.--The innermost coat of the eye-ball and the one which receives visual impressions. RICKETS.--A disease of infancy characterized by softening of the bones. SECRETION.--The product of the activity of a gland. SEDIMENT.--The material which settles to the bottom of any liquid. SPERMATOZOON (plural spermatozoa).--The microscopic cell contributed by the male parent, which stimulates the ovum to begin its development. SUPPOSITORY.--A medicinal substance made into the form of a cone to be introduced into the rectum. TERM.--The time of expected delivery. THERAPEUTIC.--Concerned with the treatment of disease. THYMUS GLAND.--A structure located behind the breast bone near the root of the neck. Only traces of it are found in adult life. TISSUE.--An aggregation of similar cells in a definite fabric, as muscle, nerve, gland, etc. TUBES.--The oviducts. UMBILICAL CORD.--The structure carrying the blood vessels which pass between the placenta and the child's navel. UTERUS.--The womb: a hollow muscular organ designed to receive, protect, nourish, and expel the product of conception. VAGINA.--The canal through which the child passes from the uterus into the world.