HAEMOPHILIA, the medical term for a condition of the blood, particularly deficiency of blood platelets, and possibly also of the vascular system, often running in families, the members of which are known as "bleeders," characterized by a disposition towards bleeding, whether with or without the provocation of an injury to the tissue. When this bleeding is spontaneous it comes from the mucous membranes, especially from the nose, but also from the mouth, bowel, and bronchial tubes. Slight bruises are apt to be followed by extravasations of blood into the tissues; the swollen joints (knee especially) of a bleeder are probably due, in the first instance, to the escape of blood into the joint cavity or synovial membrane. It is always from the smallest vessels that the blood escapes, and may do so in such quantities as to cause death in a few hours. Haemophilia occurs almost exclusively in males but is transmitted by the females of a family.