the summaries of the large amount of data in these researches,
I acknowledge with gratitude the great assistance rendered by
my associates, Dr. D. H. Dolley, Dr. H. G. Sloan, Dr. J. B. Austin,
and Dr. M. L. Menten.[*]


[*] From the H. K. Cushing Laboratory of Experimental Medicine,
Western Reserve University, Cleveland.


The scope of this paper may be explained by a concrete example.
When a barefoot boy steps on a sharp stone there is an immediate discharge
of nervous energy in his effort to escape from the wounding stone.
This is not a voluntary act. It is not due to his own personal experience--
his ontogeny--but is due to the experience of his progenitors
during the vast periods of time required for the evolution
of the species to which he belongs, _i. e_., his phylogeny.
The wounding stone made an impression upon the nerve receptors
in the foot similar to the innumerable injuries which gave origin
to this nerve mechanism itself during the boy's vast phylogenetic or
ancestral experience. The stone supplied the phylogenetic association,
and the appropriate discharge of nervous energy automatically followed.
If the sole of the foot be repeatedly bruised or crushed by a stone,
shock may be produced; if the stone be only lightly applied,
then the consequent sensation of tickling causes a discharge of
nervous energy. In like manner there have been implanted in the body
other mechanisms of ancestral or phylogenetic origin whose purpose
is the discharge of nervous energy for the good of the individual.
In this paper I shall discuss the origin and mode of action of some
of these mechanisms and their relation to certain phases of anesthesia.