THE ACTIVE FORCES OF LIVING ORGANISMS 45 



plasm at the same time that the changed reaction 

 lessens their affinity for oxygen.'* 



Since every increase of blood-pressure must per- yariations 

 force mean an increase of oxygen pressure round the tension of 



•'^ ^ . . the ether 



nerve-cell, we may suppose that with every mspira- as the 

 tion fresh molecules of oxygen are squeezed into its the 

 substance, and passing amongst the granules of which action in a 

 it is composed, oxidize, or become allied with some ^^iX' 

 of the elements present. Whilst at each increase in 

 the supply of oxygen to the nerve-cell some of the 

 molecules of the latter break up and are got rid of, 

 the remaining ones may be supposed to come under 

 the influence of a vibratory wave, the character of 

 which is determined by the degree of oxidation. This 

 wave is transmitted from the cell to the periphery in 

 the case of an efferent nerve, probably by molecular 

 movement in the nerve-fibre. But at the same time 

 that this molecular transmission takes place a second 

 event occurs : the molecules of the nerve-cell are 

 everywhere surrounded by ether, and along the 

 nerve-fibre to the periphery there is also a stratum 

 of ether. The movement of the molecules is there- 

 fore communicated to this other medium in which 

 certain variations of tension make themselves felt. 

 These variations are what is termed ' the current of 

 action ' or ' negative variation.' 



In addition to variations of blood -pressure, the The influ- 

 ence of 

 degree of oxidation is influenced by other factors, as, functional 



activity on 

 * Sir T. Lauder Branton, Introduction to ' Modern Thera- j?m^''°" 

 peutics,' pp. 112, 113. 



