face, the scalp, and the
structures of the head generally, most of them derived from one great
pair of nerve-trunks, the so-called _Trigeminus_, or fifth pair of
cranial nerves. Strange as it may seem, the brain substance is
comparatively insensitive to pain, and the acutest pain of an operation
upon it, such as for the removal of a tumor, is over when the skin and
scalp have been cut through. These poisons, of course, go all over the
body, wherever the circulation goes, but they produce their promptest
and loudest pain outcry, so to speak, in the region where the nerves are
most exquisitely sensitive. When your head aches, nine times out of ten
your whole body is suffering, but other regions of it are not able to
express themselves so promptly and so clearly.

These newer and clearer views of the nature of headache dispose at once
of some of the most time-honored controversies in regard to its nature.
In my student-days one of the most hotly debated problems in medicine
was as to whether headaches were due to lack of blood (anaemia) or excess
of blood (hyperaemia) in the brain. Few things could have been more
natural for both the sufferer in, and the observer of, a case of
throbbing, bursting headache, where every pulse-beat is registered as a
thrill of agony, than to draw the conclusion that the pain was due to a
huge engorgement and swelling of the brain with blood, resulting in
agonizing pressure against its rigid, bony skull-walls.

One of the most naive and vivid illustrations of this conception of
headache is the remedy adopted for generations past, in this all too
familiar and distressing condition, by the Irish peasantry. It consists
of a band or strip of tough cloth, or better, of twisted or plaited
straw, which is tied around the head and then tightened vigorously by
means of a stick inserted tourniquet fashion. This is believed to
prevent the head, which is aching "fit to split," from actually bursting
open, and is considered a cure of wondrous merit through many a
countryside. Ludicrous as is the reason which is gravely assigned for
its use, it does, in some cases, greatly relieve the pain, a fact which
we were entirely at a loss to account for until our later knowledge
showed us that the pain, instead of being inside the skull, was outside
of it in the sensitive nerves supplying the scalp. By steady pressure of
this sort upon the trunks of these nerves, pressing them against the
bone, they can be graduall