be admissible, but eminently desirable. It is
more especially of recent years that a laudable attempt to differentiate
the various etiological factors involved in different forms of headache
has been made. In 1832 Dr. James Mease, of Philadelphia published a
monograph on "The Cause, Cure, and Prevention of the Sick Headache,"
which is substantially a treatise on the dietetics of this particular
form of headache. The work, however, is conspicuously lacking in those
philosophical qualities which are so necessary to a true understanding
of the questions involved. Dr. E.H. Sieveking published in 1854[1] a
most interesting paper on "Chronic and Periodical Headache." The views
therein expressed are remarkable for their succinct and thoroughly
scientific elucidation of the two great physiological principles
involved in the consideration of by far the greater majority of
instances of cephalalgia. I refer namely to the importance ascribed by
this eminent physician to the fluctuations of the blood-stream within
the cranial vault. In speaking of this subject Dr. Sieveking says:
"Nothing is of more importance in reference to the pathology and
therapeutics of the head than clear and well-defined notions on the
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,