unanswered.

Haller's greatest contribution to medical science was his famous
doctrine of irritability, which has given him the name of "father
of modern nervous physiology," just as Harvey is called "the
father of the modern physiology of the blood." It has been said
of this famous doctrine of irritability that "it moved all the
minds of the century--and not in the departments of medicine
alone--in a way of which we of the present day have no
satisfactory conception, unless we compare it with our modern
Darwinism."[1]

The principle of general irritability had been laid down by
Francis Glisson (1597-1677) from deductive studies, but Haller
proved by experiments along the line of inductive methods that
this irritability was not common to all "fibre as well as to the
fluids of the body," but something entirely special, and peculiar
only to muscular substance. He distinguished between irritability
of muscles and sensibility of nerves. In 1747 he gave as the
three forces that produce muscular movements: elasticity, or
"dead nervous force"; irritability, or "innate nervous force";
and nervous force in itself. And in 1752 he described one
hundred and ninety experiments for determining what parts of the
body possess "irritability"--that is, the property of contracting
when stimulated. His conclusion that this irritability exists in
muscular substance alone and is quite independent of the nerves
proceeding to it aroused a controversy that was never definitely
settled until late in the nineteenth century, when Haller's
theory was found to be entirely correct.