These observations lead naturally to the question, May not acidity of itself be the actual final cause of death? We believe that it may be so from the facts that--(1) The intravenous injection of certain acids causes death quickly, but that convulsions do not occur, since the voluntary muscles lose their power of contraction; and (2) the intravenous injection of acids causes extensive histologic changes in the brain, the adrenals, and the liver which resemble the changes invariably caused by activation of the kinetic system (Figs. 74 and 75). In view of these facts may we not find that anesthesia and many instances of unconsciousness are merely phenomena of acidity? As has been stated already, we have found that the H-ion concentration of the blood--its acidity--is increased by alcohol, by ether, and by nitrous oxid. In addition our tests have shown that under ether the increase of the H-ion concentration--acidity--is more gradual than under nitrous oxid, an observation which accords well with the fact that nitrous oxid more quickly induces anesthesia than does ether. Further striking testimony in favor of the hypothesis that the production of acidity by inhalation anesthetics is the method by which anesthesia itself is produced is found in the fact that although lethal doses of acid cause muscular paralysis, yet this paralysis may be mitigated by adrenalin--which is alkaline. This observation may explain in part the remarkable success of the method of resuscitation devised by me, in which animals "killed" by anesthetics and asphyxia are revived by the use of adrenalin. In animals under inhalation anesthesia Williams found that no nerve-current could be detected by the Einthoven string galvanometer, a fact which might be explained by postulating that nerve-currents can flow from the brain to the muscles and glands only when there is a difference of potential. Any variation from the normal alkalinity of the body must change the difference in potential. Since the nerve-currents in animals under anesthesia are not demonstrable by any apparatus at our command, and since anesthesia produces acidity, then we may infer that acidity reduces the difference in potential. As long as there is life, a galvanometer of sufficient delicacy would perforce detect, a nerve-current until the acidity increased to such a point as to reduce the difference in potential to zero-- the point of death. If at this point a suitable alkali-- adrenalin solution--can be introduced quickly enough, the vital difference in potential may be restored and the life processes will be renewed. Bearing especially on this point is the fact that if adrenalin in sufficient quantities be administered simultaneously with an acid, it will not only prevent the fall in blood-pressure usually caused by the acid, but will also prevent the histologic changes in the brain, adrenals, and liver which are usually caused by the intravenous injection of acids.