Median line. An ideal line dividing the body longitudinally.

Medulla oblongata. The upper or cranial portion of the spinal cord.

Meningitis. Inflammation of the meninges or membranes of the brain.

Menorrhagia. Profuse menstruation.

Mesentery. A portion of the peritoneum attached to the small intestines.

Metastasis. A sudden removing of disease from one part to another.

Metritis. Inflammation of the womb.

Miasm. Infection floating in the air.

Micturation. The act of urinating, or evacuating the bladder.

Minim. The smallest liquid measure; a drop.