THE PROCESSES OF DEPRESSION 241 



lar to those characteristic of strychnine poisoning. Very soon, 

 however, this state of high excitation is followed by one of de- 

 pression, in which no response to stimuli can be obtained. The 

 animal remains entirely motionless in any position in which it is 

 placed, in the same manner as a frog whose nerve centers have 

 been completely exhausted by strenuous activity. On the basis of 

 our knowledge of the role played by the deficiency of oxygen in 

 the bringing about of exhaustion the thought arose, if in this heat 

 depression exhaustion might not likewise be the result of oxygen 

 deficiency. This assumption has been most strikingly confirmed 

 by the investigations of Winterstein. It has been demonstrated 

 that recovery of the animal in a state of heat depression cannot 

 be obtained by mere cooling, but is only brought about when at 

 the same time a renewed oxygen supply is provided. For instance, 

 a frog is depressed in the warm chamber and even when a 

 strychnine injection has been introduced, does not show the 

 slightest reaction to stimuli. In the warm water bath artificial 

 circulation is now applied in the previously described manner with 

 an oxygen-free saline solution at 30° C, so that the blood is dis- 

 placed and thus the renewed oxygen supply to the nervous centers 

 prevented. The animal can now be cooled and the warm saline 

 solution be replaced by a cooled one without the least recovery 

 taking place. If, however, blood of the ox with contained oxygen 

 is substituted for the oxygen-free saline solution, the frog shows 

 signs of recovery within a few minutes and after ten or fifteen 

 minutes responds as a result of the strychnine to the merest touch 

 with tetanic contractions of the whole body. By modifying these 

 methods of investigation to a certain extent Bondy^ has confirmed 

 these results to the fullest extent. Later Winterstein by quanti- 

 tative determinations of oxygen consumption on medusae showed 

 that at 30-35° C, at which temperature heat depression sets in, 

 the consumption of oxygen shows an increase of about three and 

 a half times compared to that in a temperature of 11-12° C. 

 These facts show that we have in heat depression a process which, 

 as far as its genesis is concerned, is completely analogous to that 



1 Oskar Bondy: "Untersuchiingen fiber die Sauerstoffaufspeicherung in den Ner- 

 venzentren." Zeitschr. f. allgem. Physiol. Bd. II, 1904. 



