PREFACE xi 



is to say, modify the nervous rhythm. At first sight it 

 may be difi&cult to conceive how this is brought about, 

 for it is very improbable that there is actual contact 

 between the nerve-endings and the salt or the iron 

 contained in the bath. But if we suppose, as we have 

 reason to, that a stratum of ether lies between the 

 nerve-endings and the chemical substance, whatever 

 it may be, that the nerve-endings are continually 

 undergoing a certain delicate vibration due to the 

 force generated in the nerve-cell in the process of its 

 metabolism, and, further, that this force causes, as it 

 were, waves or impulses in the stratum of ether which 

 dash up against the particles of salt or iron and come 

 back bearing the character of these substances and 

 thus transmitting it to the nerve-endings and through 

 them to the nerve-cells, then we shall understand 

 how the nervous rhythm may be modified and the 

 physiological processes depending on it altered, 

 although nothing whatever has been added to the 

 body. We can also comprehend how it is that even 

 an insoluble drug, such as calomel, can produce so 

 marked an effect, and how an insoluble preparation 

 of arsenic, such as dentists commonly use, causes 

 death in the nerve of a tooth. Transmission in such 

 cases is, moreover, very similar to the phenomenon 

 of sight if we suppose light itself to be due to ethereal 

 movement. 



In speaking of the action of insoluble drugs and of 

 chemical substances held in solution in baths as being 

 of a dynamic nature, only a very limited portion of 



