246 IRRITABILITY 



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 re- 

 place the oxygen-free saline solution containing alcohol by blood 

 rich in oxygen, containing alcohol in an amount sufficient to con- 

 tinue 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 dis- 

 posal 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 strych- 

 ninized 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 con- 

 sumed 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 indi- 

 cator 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. 1 

 These were carried out with alcohol, ether, chloroform and also 

 carbon dioxide. His experiments have shown in the most 

 uniform manner that, in spite of the requirement of oxygen by 

 the centers being increased to its highest extent, and notwith- 

 standing the most ample oxygen supply during narcosis, after 

 cessation of the same and the introduction of an oxygen-free 

 saline solution no trace of recovery occurred, whereas after a 

 supply of oxygen was introduced tetanic contractions reappeared 



1 H. Winterstein: "Zur Kenntniss der Narkose." Zeitschr. fur allgem. Physiol. 

 Bd. I, 1902. 



