This term, which, etymologically speaking, signifies pulselessness, has been erroneously applied to that condition in which there is great deficiency of oxygen, and, as a rule, increase of carbon dioxide in the blood. The amount of oxygen entering the lungs may be reduced rapidly by strangulation, or by closure of the mouth and nostrils, as in smothering, or by sudden closure of the glottis, as by choking, or by exposure to irrespirable gases, such as carbon dioxide and chlorine, or to such a gas as carbon monoxide, which, though respirable, replaces oxygen in the blood corpuscles, or by plunging the animal into another medium, as into water or mercury, which is drowning, or by the simple withdrawal of oxygen from the air; or it may be induced more slowly by closing the air-tubes with the products of secretion, as in diphtheria or croup and laryngitis, or by paralysing the muscles of respiration, as by the action of curara, or by opening both pleural sacs simultaneously, thus preventing the lungs from following the expansion of the chest walls, or, lastly, by loss of blood. It is usually divided into three stages, the first of which, in rapidly-induced asphyxia, lasts about a minute, and is characterized by violent inspiratory efforts. Then the abdominal muscles contract powerfully, and strong expiratory efforts occur, which are succeeded by irregular spasms of the limbs, chiefly affecting the flexor muscles. The blood pressure rises to a great height, owing to the stimulation of the smaller vessels by the non-arterialized blood. In the second stage, which also lasts about a minute, the convulsive movements cease, the expiratory movements are hardly perceptible, the pupil dilates, and touching the eyeball excites no reflex movement of the lids. The blood - pressure gradually falls, and the muscles generally are relaxed. In the third stage, which lasts two or three minutes, the inspiratory efforts become more feeble, and only take place at long intervals spasmodically, the extensor muscles are convulsed, the head is thrown back, and death closes the scene.