THE REFRACTORY PERIOD AND FATIGUE 181 



It was found by Hermann^ in 1867 and confirmed by Mademoi- 

 selle Joteyko^ in Richet's laboratory, that the isolated muscle of 

 the frog, which was completely nonirritable as the result of 

 fatigue, does not regain irritability in an oxygen-free medium, 

 but does so when oxygen is introduced. The previously de- 

 scribed experiments of artificial circulation in the frog show 

 clearly how dependent the centers are upon the oxygen supply 

 for the restoration of irritability. In consequence of the strych- 

 nine poisoning the irritability of the centers is so enormously 

 increased that the "all or none law" is applicable to the centers of 

 the spinal cord under these conditions.^ These are the best condi- 

 tions for the production of fatigue. One can readily demonstrate 

 the importance of the oxygen supply for the rapidity with which 

 irritability returns after fatigue if in the strychninized frog an 

 artificial circulation is used, at the same time varying on one hand 

 the amount of oxygen, on the other the activity of the centers. If 

 a saline solution containing merely a trace of oxygen is circulated, 

 the centers recover very slowly and incompletely after every 

 fatigue. Subsequent to every reaction produced by a stimulus, 

 an increasing length of time is required until irritability is so far 

 recovered that a new stimulus can meet with response. If, how- 

 ever, a saline solution is circulated which has been saturated by 

 being shaken with oxygen and is continuously in a pure atmos- 

 phere of oxygen, recovery takes place in comparison with far 

 greater rapidity and completeness. If the supply of oxygen is 

 ample and the stimuli act at longer intervals on the frog, irri- 

 tability always is quickly restored in the periods of rest between 

 the stimuli. With continuous stimulation of quickly succeeding 

 stimuli, irritability is soon completely obliterated, even though an 

 abundant oxygen supply be present, and it is not until a pause is 

 interpolated that oxygen is capable of bringing about a recovery. 

 By manifold variations of these experiments the connection 

 between fatigue and the refractory period can be more and more 



1 Hermann : "Untersuchungen fiber den Stoffwechsel der Muskeln ausgehend vom 

 Gaswechsel derselben." Berlin 1867. 



ZJoteyko: "La fatigue et la respiration elementaire du muscle." Paris 1896. 



3 Julius Vessi: "Zur Frage des Alles oder Nichts Gesetzes beim Strychninfrosch." 

 Zeitschr. fur allgem. Physiologic Bd. XII, 1911. 



