1. _Pressure on the Vessels._—The red and livid hue of the face of persons killed by hanging, very naturally induced a belief that _Apoplexy_[42] was the immediate cause of death; while it is evident that the pressure on the jugular veins must necessarily so prevent the return of blood to the heart, as to produce an accumulation in the vessels of the brain: _Dr. Hooper_ has a preparation of the brain of an executed criminal, in which blood is seen extravasated among the membranes; and various other cases have occurred, where dissection has clearly demonstrated the existence of those vascular congestions and sanguineous effusions, upon which apoplexy is supposed to depend; but this merely goes to prove that apoplexy occasionally takes place from hanging; it does not establish the fact of its being the common cause of death on such occasions.[43] _Gregory_ made the following experiment to shew that it is to the interception of air that death is to be attributed; after having opened the trachea of a dog he passed a slip knot round the neck, above the wound; the animal, though hanged, continued to live and respire, the air was alternately admitted and easily expelled through the small opening; but as soon as the constriction was made below the orifice, the animal perished. _Mr. Brodie_ hanged a dog, and as soon as it became insensible, the trachea was opened below the ligature, upon which he breathed, and his sensibility returned. 2. _Pressure on the Nerves of the Neck._ Although the pressure of a ligature on the nerves of the neck cannot be considered as the immediate cause of death in hanging, yet _Mr. Brodie_ has very justly observed, that if the animal recovers of the direct consequence of the strangulation, he may probably suffer from the effects of the ligature upon the nerves afterwards. _Mr. Brodie_ passed a ligature under the trachea of a Guinea pig, and tied it tight on the back of the neck with a knot; the animal was uneasy, but nevertheless breathed and moved about; at the end of fifteen minutes the ligature was removed; on the following morning, however, the animal was found dead. On dissection no preternatural appearances were discovered in the brain, but the lungs were dark and turgid with blood, and presented an appearance similar to that which is observed after the division of the nerves of the eighth pair; I do not, observes _Mr. Brodie_ (_Manuscript Notes_) positively conclude from this experiment that the animal died from an injury inflicted upon the nerves of the eighth pair, but I think that such a conclusion is highly probable; and it becomes an object of inquiry whether a patient having recovered from hanging, may not, in some instances, die afterwards from the injury of the _par vagum_.