[216] For the very extensive literature on this subject see _Reicher_: “Chemischexperimentelle Studien zur Kenntniss der Narkose.” Zeitschr. f. klinische Medicin Bd. 65, 1908. [217] _Heaton_: l. c. In view of this knowledge of the influence of narcotics on oxygen exchange it may be considered as a firmly established fact, that a process of depression is developed during narcosis, which can be classified with the large group of depressions, resulting from deficiency of oxygen. This is followed by the important problem, is it possible to attribute the whole series of alterations, produced by the narcotic, solely to this _one_ factor? In other words, is narcosis the result of acute suppression of the oxydative processes? If the individual symptoms which characterize narcosis are investigated from this point of view, one must indeed confess that they are all readily understood when regarded as the results of suppression of the oxydative processes. Indeed, the disappearance of the perceptible vital activities, the decrease of irritability, the restriction of the conduction of excitation, the continuance of an anoxydative breaking down, the recovery on cessation of narcosis, provided oxygen is present, etc., in short, all the characteristics of narcosis so far known must be expected and _demanded_ if a suppression of the oxydative processes exists during narcosis. There is only _one_ point which at the first glance would not seem to agree entirely with the assumption. This is the fact that depression sets in with a relatively greater rapidity in narcosis than when the supply of oxygen is completely withdrawn. Depression of the centers in the spinal cord, which begins in about five to ten minutes after artificial circulation of an oxygen-free, alcohol-containing, saline solution, is not brought about for more than an hour when the same saline solution but without alcohol is introduced. This difference is still more strikingly apparent in the nerve. The same degree of depression, which is produced in the nerve in a nitrogen-ether mixture within about _five_ minutes, is not reached in pure nitrogen without ether until after the lapse of from _two_ to _four_ hours. In order to investigate this relation somewhat more closely I have questioned if it is possible for a living system, which has been narcotized to a certain extent, to regain its irritability in a completely oxygen-free medium, if cessation of the narcosis takes place after a period essentially shorter than the time of asphyxiation of the system under equal conditions. If the depression of narcosis is founded exclusively on asphyxiation, it would be expected that no recovery could occur. Experiments which I have made on the spinal cord centers as well as on the peripheral nerves have, however, demonstrated exactly the contrary. If a frog is subjected to an artificial circulation of an oxygen-free saline solution containing 5 per cent. of alcohol until