THE REFRACTORY PERIOD AND FATIGUE 171 



stances. If we assume that at the moment when the entire amount 

 of blood is removed from the vascular system, no oxygen remains 

 in the cells of the spinal cord and muscle, then disintegration of 

 the living substance could from this instant take place exclu- 

 sively anoxydatively, and there would be no further oxydative 

 breaking down into carbon dioxide and water. The energy pro- 

 duction compared in equal number of molecules, taking the 

 figures of Lesser for the fermentation of sugar, would approxi- 

 mately amount to about 3.8 per cent, of that of the energy pro- 

 duction in the oxydative disintegration of dextrose into carbon 

 dioxide and water. In reality, however, the tetanic convulsions 

 are at first exactly as violent as in the frog with a normal circu- 

 lation. There simply remains the assumption, therefore, that 

 either the disintegration as soon as it becomes anoxydative in- 

 volves relatively greater number of molecules than would be the 

 case if it were oxydative in nature, or to suppose that even 

 after the complete displacement of the blood a certain, though 

 relatively small, amount of oxygen is present in the cells which 

 for a short time suffices for the taking place of oxydative disin- 

 tegration and with this an almost maximal production of energy 

 which naturally decreases as the oxygen is consumed. It seems 

 to me that the latter supposition contains more probability than 

 the first. To return, however, from this observation to a further 

 consideration of the animal we are studying, we see how the 

 complete tetanic convulsions in the refractory period which we 

 assumed to be .1 second are gradually transformed into incom- 

 plete tetanus. After a time the tetanic convulsions become shorter 

 after each stimulus (Figure 32, B) and permit us to distinguish 

 their individual movements, even though the latter at first succeed 

 each other still very rapidly. Gradually this incomplete tetanic 

 convulsion assumes the form of a short series of individual con- 

 tractions, distinctly separated from each other and soon a stage is 

 reached in which each reaction to a peripheral stimulus consists 

 merely in a single contraction. (Figure 32, C.) The refractory 

 period is, however, even now less than a second. Nevertheless, 

 with a further continuation of the experiment, the refractory 

 period becomes more and more prolonged, so that stimuli succeed- 



