THE PROCESSES OF DEPRESSION 245 



tating stimuli produce a greatly weakened excitation, and that 

 in deep narcosis no perceptible response is obtained. This can 

 readily be ascertained in the various forms of living substance. 

 According to the previous observations on the inseparable rela- 

 tions between conduction of excitation and irritability, it is self- 

 evident that with decrease of irritability there must be a corre- 

 sponding decrease in the capability of the conduction of excita- 

 tion from the point of stimulation. This decrease in conduc- 

 tivity must, therefore, be the greater the more irritability is re- 

 duced; that is, the deeper the narcosis, the greater must be the 

 decrement undergone by the wave of excitation in its extension 

 from the point of stimulation. These facts can be observed in 

 the highest perfection in the nerve, and have, as we have seen, 

 been demonstrated by the investigations of Werigo, Dendrinos, 

 Noll, Boruttau and Frohlich. 1 Upon deeper analysis of this pro- 

 cess of depression, the next task for the investigator must be the 

 ascertainment of the special components of the metabolic activity, 

 which are depressed as a result of the narcotic. 



As a consequence of the result of my investigations on fatigue, 

 the idea occurred to me to test if possibly oxygen exchange like- 

 wise undergoes depression during narcosis. The spinal cord 

 centers of the frog, which had served me in ascertaining the role 

 played by oxygen in the bringing about of the depression of 

 activity, appeared likewise a favorable object for this investi- 

 gation. 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 



1 I have previously on another occasion briefly communicated the conclusions derived 

 from the investigations made at the Gottingen laboratory by my coworkers and myself. 

 Compare: Max Verworn: "Ueber Narkose." Deutsche medicin. Wochenschrift, 1909. 



