I have dissected many bodies, in which, before death there had been a sanguineous congestion in the exterior capillary system of the face, the neck and even of the thorax. This system exhibited a remarkable engorgement and lividity in all its parts, and I have found in opening the arteries and veins, in those of the neck and head especially, a frothy blood, mixed with bubbles of air. I learnt that one of these subjects died suddenly with a convulsive affection of the pectoral muscles; I have no information respecting the others. Besides, all who have had much to do with dissecting rooms, must have seen bodies of this kind, which very soon become putrid and emit an insupportable odour. They have observed also that the air in the vessels existed previous to the putrefaction. I suspect that in all these cases death has been produced by the sudden passage of air from the lungs into the blood, which has afterwards carried it to the brain; nearly like what I have said takes place, when, in a living animal, we force much air towards the lungs, and thus drive this fluid into the vascular system. By considering these phenomena in connexion with the remarks presented above on death from the injection of air into the veins, the opinion I have advanced, will I think, be admitted, and it is besides the opinion of many other physicians. Many experiments have already been made on the dead body relative to this point. Morgagni has presented them in detail; but it is on the living that we must observe the passage of the air into the blood in order to deduce consequences which shall bear on the subject on which we are treating. We know in fact what is the influence of death on the permeability of the parts. [108] I saw, in a little girl of seven or eight years of age, an emphysema which occurred in a paroxysm of coughing, and which extended to the thorax, the abdomen and the superior part of the thighs; the swelling of the neck was so considerable, that at the moment I was called suffocation was imminent. I made, in the skin above the sternum, an opening, which very quickly produced an evacuation of the air. In five or six days, though the hooping cough continued, this little patient was entirely cured of the emphysema, which had been very near destroying her. It did not appear to me that the lungs had participated at all in the general emphysema. [109] The above experiments explain the manner in which emphysema is produced from any very violent exertion of the muscles of the chest. CHAPTER X. OF THE INFLUENCE OF THE DEATH OF THE BRAIN OVER THAT OF THE LUNGS.