48 A CHEMICAL SIGN OF LIFE 



the nerve has recovered from the first. This refractory 

 period of 1/5,000 of a second may be considerably pro- 

 longed under certain conditions, such as low temperature, 

 high temperature, asphyxiation, various drugs, and 

 certain anesthetics. Frolich prolonged this refractory 

 period by partial anesthesia and succeeded in producing 

 fatigue phenomena by repeated electrical stimulations 

 at shorter intervals than the prolonged refractory period 

 of the nerve. 



The idea that all the physiological activities are 

 composed of at least two opposing metabolic phenomena 

 was expressed by Claude Barnard and later extended by 

 Hering. Thus metabolic activities are considered as 

 consisting of two phases, namely, a breaking down, or 

 katabolic, and a building up, or anabolic, phase. That 

 two such phenomena are involved in nervous metabolism 

 and are closely connected with the phenomena of fatigue 

 may be shown by the use of certain drugs in connection 

 with electrical changes and refractory periods. Waller 

 observed that protoveratrin slows up one of the electrical 

 changes (positive variation) of the nerve, while the 

 other (negative variation) is little influenced. He 

 contended accordingly that this drug does not alter 

 katabolic changes of the nervous metabolism but re- 

 tards the anabolic activity to a considerable degree. It 

 is by its anabolism that the nerve is restored to its nor- 

 mal state after the passage of the impulse. Since the 

 pharmacological action of protoveratrin and yohimbin 

 on muscle are known to be very similar, Tait concludes 

 from the study of the effect of yohimbin on the refractory 

 period of the nerve that these drugs must attack nerves 

 in a similar manner. Yohimbin, in other words, retards 



