[205] I have previously on another occasion briefly communicated the conclusions derived from the investigations made at the Göttingen laboratory by my coworkers and myself. Compare: _Max Verworn_: “Ueber Narkose.” Deutsche medicin. Wochenschrift, 1909. As a consequence of the result of my investigations on fatigue, the idea occurred to me to test if possibly oxygen exchange likewise undergoes depression during narcosis. The spinal cord centers of the frog, which had served me in ascertaining the rôle played by oxygen in the bringing about of the depression of activity, appeared likewise a favorable object for this investigation. Indeed, the question if consumption of oxygen takes place during narcosis, could be experimentally determined in direct connection with the investigations on fatigue. This was based on the following consideration. If an oxygen-free saline solution is introduced into the aorta of a frog and in order to increase the activity of the spinal cord centers to the maximum the animal is poisoned with strychnine, after a very short time complete exhaustion takes place as a result of oxygen deficiency. This exhaustion can only be removed by the introduction of oxygen. In this condition the oxygen requirement of the centers is enormously increased. If the centers are narcotized by adding a narcotic to the oxygen-free circulating fluid in amounts which, as experience has found, would produce complete loss of reaction in the normal animal, for example, about 5 per cent. of alcohol, it can then be tested if, in this state of narcosis, the centers are capable of oxygen consumption. It is merely necessary to replace the oxygen-free saline solution containing alcohol by blood rich in oxygen, containing alcohol in an amount sufficient to continue the narcosis, but supplying an abundance of oxygen. If, after this artificial circulation has lasted for a sufficient period, the blood is then displaced by an oxygen-free saline solution containing alcohol, and then this, in turn, is replaced by an oxygen- and alcohol-free saline solution, so that cessation of the narcosis is now produced, it can be ascertained by the responses of the animal if consumption of the oxygen, when at the disposal of the centers during narcosis, has taken place or not. If the former is the case, then on the cessation of narcosis reflex contraction must occur in the same manner as in every strychninized frog totally exhausted by oxygen deficiency and into which a saline solution containing oxygen is reintroduced. If during narcosis, on the other hand, oxygen has not been consumed by the centers, depression must continue to be present after cessation of narcosis. Testing the recovery of the animal on the introduction of blood, rich in oxygen, serves as an indicator for the vital activity and capability of recovery of the centers. A great number of experiments based on this scheme of investigation were undertaken at my request by _Winterstein_.[206] These were