THEORY OF A NERVOUS ETIIER. 
381 > 
material medium, the chemical composition of which he has 
not yet discovered. Again, when I speak of a nervous ether, I 
do not convey that the ether is existent in nervous structure 
only : I believe, truly, that it is a special part of the nervous 
organisation ; but as nerves pass into all structures that have 
capacities for movement and sensibilities, so the nervous ether 
passes into all such parts ; and as the nervous ether is, accord- 
ing’ to my view, a direct product from blood, so we may look 
upon it as a part of the atmosphere of the blood. 
The theory of the existence and influence of a nervous fluid 
is old. The earliest practical neuro-physiologists seized upon 
it at once as affording the only explanation of many vital 
phenomena. Willis, who was the leader of modern neuro-phy- 
siology, gave the cue, and after him, up to the time of Gralvani, 
every school taught the theory. “ There exists,” said the masters 
— 66 there exists in the nervous system a distinct fluid, a liquid 
which proceeds from the centres towards and to the extremities 
of the nervous system. The nervous centres (the brain in- 
cluded) are thus positively glands ; they secrete the nervous 
fluid and pour it out by the nerves. As bile is secreted by the 
liver and poured forth, so is the nervous fluid secreted by its 
centres and poured forth by the nerve ducts.” Alexander 
Munro, in 1783, sums up the argument clearly and tersely, to 
the effect that the nerves are tubes or ducts conveying a fluid 
secreted in the brain, the cerebellum, and spinal marrow. 
To the physiologists from the time of Willis (who lived, by 
the way, in the reign of Charles II.) and to those who followed 
him up to the time when Gralvani made his first observations 
on so-called animal electricity (1790) this hypothesis of a 
nervous fluid sufficed to explain the varied phenomena of 
nervous function : the fluid was supposed to convey the vibra- 
tions of the outer world to the inner centres of the animal 
body ; the fluid governed secretion ; the fluid was the channel 
by which, or rather through which, the volitional powers of the 
animal were brought to bear on the muscular mechanism. 
Nor must it be ignored that the arguments employed in 
support of the theory were sensible and were supported by 
experimental facts. “ When,” argued the maintainers of the 
theory — “ when we cut a nerve across and bring its parts again 
into contiguity, we do not restore the office of the nerve 
immediately, nay, the influence of the nerve beyond the 
incision is generally not restored : when we compress a nerve 
we produce numbness by the compression ; and when, by 
repeated slight compressions of a nerve, we cause repeated 
contractions of the muscles fed by the nerve, we prove that 
the impulse is exerted on matter which admits of being 
affected by simple pressure .” 
