THEOEY OF A NEE VO US ETHEE. 
By DE. RICHARDSON, F.R.S. 
I N my course of experimental lectures on medical science 
delivered during the last winter session, I broached a modi- 
fication of the old and well-nigh obsolete theory of the exist- 
ence of a nervous fluid ; and I have since reduced to some form, 
in a published lecture, the ideas I wished to set forth.* It has 
been curious to me to observe the different lights in which this 
effort has been viewed by men of different phases of thought 
and knowledge. Some physicists have accepted that the theory 
suggests the existence of an intermediate agency between the 
matter of living bodies and the forces by which the matter is 
moved — an agency essential to the correct understanding of the 
relations coexisting between the living matter and force. 
Others have thought the theory obscure and retrogressive, a 
kind of retreat into the bosom of Van Helmont, and of those 
fanciful heroes of Lord Lytton, who, still professing Helmontism 
as an article of scientific, and I had almost said moral faith, 
proclaim life to be “ a gas.” Lastly, certain enthusiastic writers, 
and, as they call themselves, experimenters, have actually laid 
hold of the theory to support modern spiritualism, and its idola 
of the theatre. 
To commence with the last of these critics, I need scarcely 
say, in relation to them, that there is nothing in my mind 
bearing in the remotest degree on their arguments. I speak 
only of a veritable material agent, refined, it may be, to the 
world at large, but actual and substantial : an agent having 
quality of weight and of volume ; an agent susceptible of 
chemical combination, and thereby of change of physical state 
and condition ; an agent passive in its action, moved always, 
that is to say, by influences apart from itself, obeying other 
influences ; an agent possessing no initiative power, no' ms, or 
energia natures , but still playing a most important, if not a 
* Medical Times and Gazette , May 6, 1871. 
