iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 231 



atmosphere, and the current of indifferent gases continued for 

 twenty-five minutes, the nerve does not recover. But if oxygen is 

 passed through the gas chamber there is a preceptible recovery in 

 three to six minutes, which becomes complete in a few moments. 



These results show that the vitality of nerve depends on a 

 definite supply of oxygen. Its 

 comparative inexhaustibility 

 under normal conditions is due 

 to the fact that at ordinary 

 temperature, in presence of 

 atmospheric air, it obtains -all 

 the oxygen essential to its 

 functions. As we have seen, 

 both v. Baeyer and Frohlich 

 demonstrated unmistakable 

 phenomena of nerve - fatigue 

 in an atmosphere deprived of 

 oxygen. 



Von Baeyer's experiments 

 were extended and completed 

 by Fr. W. Frohlich (1903), who 

 found that asphyxiated and 

 anaesthetised nerve is incap- 

 able of recovery by assimilating 

 oxygen, confirming the results 

 of Hans Winterstein for nerve- 

 centres (infra]. Frohlich then 

 studied the effects of duration 

 of oxygen supply on the re- 

 covery of asphyxiated nerve. 

 With prolonged passage of 

 oxygen he found an initial 

 rise of excitability up to the 

 normal height; a further supply 

 of oxygen produced no further 

 rise of excitability, but in- 

 creased the duration of a second 

 asphyxia. 



Von Baeyer's experiments 

 were repeated by Boas (1904), 



who placed the nerve in an atmosphere of pure hydrogen and 

 in vacuo, with the same results. 



Thunberg (1904) showed that the consumption of oxygen and 

 production of carbonic acid in nerve can be demonstrated directly 

 by chemical analysis. By means of a micro-respiratory method he 

 was able to measure oxygen intake and carbonic acid output from 

 excised bits of rabbit's nerve. 



Fio. 146. Von Baeyer's method of demonstrating 

 the effect of gases on a length of nerve. a,U-tube 

 ending in a bulb with a little water to saturate 

 the gas passing through it ; the tube is enclosed 

 in a kind of water-bath by which the temperature 

 of the gas can be raised as desired ; 6, gas 

 chamber into which the nerve is introduced 

 through the side aperture c, and where it can 

 be excited by means of platinum electrodes 

 soldered in at d ; e, vent for gas ; /, rubber cork 

 through which the bulb of a thermometer can 

 be introduced into the chamber. 



