186 IRRITABILITY 



vVV\Aa^^ 



V 



Scheme showing course of fotigue (plain line) and recovery (dotted line) of the nerve 

 as it is manifested on testing the irritability with tetanic stimuli, when fatigue and 

 recovery alternate at equal intervals. The curve shows at the beginning an apparent 

 increase of irritability corresponduig to the "Treppe" of the muscle. (After Thorner.) 



B 



Fig. 37. 



Scheme showing course of fatigue (plain line) and recovery (dotted line) on testing the 

 irritability of the nerve by single induction shocks. In fotigue irritability sinks at first 

 rapidly, then more and more slowly until a state of equilibrium is reached. Recovery 

 shows the same in reverse succession. (After Thomer.) 



interrupted, whereas a complete recovery could not take place 

 unless a supply of oxygen was introduced. (Figure 38.) This 

 fact is in perfect accordance with the relations found by Ver- 

 worn, Lipschiitz, in fatigue of the nervous centers. It is the 

 expression for the accumulation and removal of fatigue sub- 

 stances, the depressing eifect of which Ranke^ first established 

 for the fatigued muscle. The fact that the nerve could also par- 

 tially recover in an atmosphere of nitrogen would seem to like- 

 wise contain the proof that among the fatigue substances products 

 in the form of gas must be present. It is probable that an escape 

 of carbon dioxide has taken place. 



1 Ranke: 'IJntersuchungen uber die chemischen Bedingungen der Ermudung des 

 Muskels." Arch. f. Anat. u. Physiol. 1863 u. 1864. 



