physiological subject of the circulation within the cranium; for, among
the various sources of medical skepticism, no one is more puzzling or
more destructive of logical practice than a contradiction between the
doctrine of physiology and the daily practice of medicine."

[Footnote 1: On Chronic and Periodical Headache, by E.H. Sieveking,
M.D., _Medical Times and Gazette_ London, August 12, 1854.]

What Dr. Sieveking said in 1854 holds equally good to-day; and, indeed,
the position then taken has received substantial indorsement through the
positive results of more recent experimental physiology. Conspicuous in
this connection are the inductive researches of Durham, Fleming, and
Hammond, touching the modifications in the cerebral circulation during
sleep and wakefulness. By these experiments it has been conclusively
proved that the amount of blood in the brain is decreased during sleep
and increased during wakefulness. More, recently I have had occasion to
confirm the experiments of Fleming in this direction, and have published
the results of those researches in various papers and articles.[1] "What
Hippocrates said of spasm," says Dr. Sieveking, "that it results either
from fullness or emptiness, or, to use more modern terms, from hyperæmia
or anæmia, applies equally to headache; but, to embrace all the causes
of this affection we must add a third element, which, though most
commonly complicating one of the above circumstances, is not necessarily
included in them, namely a change in the constitution of the blood."
While I agree with Dr. Sieveking as regards the importance to be
ascribed to the first two factors--cerebral hyperæmia and anæmia, in the
production of the group of symptoms known as "headache,"--I fail to
perceive why especial prominence should be given to the third condition
mentioned by Dr. Sieveking. Indeed, I am quite unable to imagine how the
periodical, and more especially the intermittent form, of headache is to