The final cause of death will depend on: 1. The suddenness and completeness of interference with the access of air; asphyxia. 2. Pressure on the large veins of the neck, preventing the return of blood from the head, causing congestion of brain and coma. 3. Pressure on the large arteries of the neck, preventing access of blood to the brain; causing anæmia of the brain and syncope. 4. Injury to spinal cord or pneumogastric nerves or all of them; causing paralysis. A combination of numbers 1 and 2 is usually found in suicidal hanging; and probably all of them in homicidal and judicial hanging. The more protected the air-passages are from pressure the greater part will coma or syncope have in the cause of death.
Mackenzie,[802] as the result of examination of 130 suicidal hangings, says that 119 died of asphyxia, 8 of asphyxia and apoplexy, 2 of syncope, and 1 of apoplexy alone. Coutagne[803] thinks œdema of the lungs, “œdema carminé,” has an important part in causing death.
The following conditions tend to produce asphyxia: a tight ligature, or a loose ligature above the hyoid bone. To produce coma, a loose ligature pressing against the hyoid bone or larynx, especially a cretified larynx. To both asphyxia and congestion of brain, a ligature just beneath the lower jaw, or around lower part of neck.
Hofmann[804] states that when the ligature is placed between the larynx and hyoid bone, the base of the tongue is pushed upward against the posterior wall of the pharynx, completely stopping respiration and causing asphyxia. Taylor[805] states that if the rope presses on or above the larynx, the air-passages are not so completely closed as when pressure is below the larynx. In the latter case death would be immediate; in the former a slight amount of respiration might continue. The instantaneous loss of consciousness is due, not to asphyxia alone, but to compression of the large vessels, especially the carotids, against the transverse processes of the vertebræ, causing rupture of the middle and inner coats, and at the same time compression of the jugular veins and pneumogastric nerves. Immediate unconsciousness will almost certainly follow compression of the pneumogastrics. He also believes that the loss of consciousness and of power of self-help occur at the moment that the noose is tightened around the neck. There is no record of any one who attempted suicide by hanging seeking to recover himself, although no doubt some would have done so if the speedy unconsciousness had not prevented. Hofmann mentions the case of a man who was found hanging, and with a loaded revolver in his hand, apparently having intended to shoot as well as hang himself, but lost consciousness before he had time to discharge the revolver. According to him the causes of death are three: occlusion of the air-passages, interruption of passage of blood to brain, and compression of pneumogastric nerves.
Von Buhl[806] experimented on cadavers and concluded that in hanging, the epiglottis and arytenoids are pressed over the glottis, and the tongue and the œsophagus against the vertebræ, causing death by apnœa. When the trachea was isolated from the vessels and tied, the air-passages below became dilated and the lungs emphysematous and anæmic. The heart continued to beat and blood to circulate.
The vertebral arteries being much smaller than the carotids, the circulatory disturbance in the brain is not adjusted with sufficient promptness. Compression of the pneumogastrics, according to Waller,[807] has caused subjects to fall to the ground as if struck by lightning. He holds that the unconsciousness in hanging is the result of the compression of the pneumogastric nerves and not of the arteries. Thanhöfer[808] knew a student who had acquired a certain dexterity in compressing these nerves. One day he compressed the two nerves, his pulse stopped and he became unconscious. Thanhöfer[809] tried bilateral compression of pneumogastrics in a young man sentenced to be executed. The pulse fell at once and the heart soon stopped; the eyes were fixed and glassy. It was some time before he regained consciousness and for two days there was malaise.
Hofmann says that the compression irritates and, in a higher degree, paralyzes the pneumogastric nerves and causes disturbance of the action of the heart.
Faure[810] denies that the constriction of the vessels of the neck has any effect in the production of symptoms[811].
Coutagne believes that the pressure on the pneumogastric nerve is a factor in causing death. He hung two dogs; in one the pneumogastric nerves were dissected out and placed in front of the ligature; this dog (No. 1) lived a quarter of an hour and died of pure asphyxia with efforts at inspiration continued to the end. The other dog (No. 2), in which the nerves were compressed, died in five minutes. In both, the abdominal organs were congested and the cavities of the heart were full. The lungs of the first were dry and uniformly red; of the second were resisting, crepitant, and quite œdematous. No subpleural ecchymoses in either. The experiments on animals by Corin[812] led him to conclude that pressure on the pneumogastrics caused increased frequency of the heart-beat and slowing of respiration. Pellier[813] considers the subject quite fully. It would appear that the pressure on the pneumogastrics disposes to stop the action of the heart and cause rapid, perhaps instant death. The pressure on the carotids causes cerebral anæmia and is then only a secondary cause. Levy[814] does not think the action of the pneumogastrics is sufficiently well known.
Tidy states that a dog lived for three hours suspended by a rope placed above an opening in the windpipe; and that Smith[815] mentions the case of a criminal who was hung; Chovet tried to save the man by making an opening in the trachea before the execution and introducing a small tube. The man was alive forty-five minutes after the drop, but could not be resuscitated, although the surgeon bled him.