y make two
pulsations for one.

Suppose the diameter of the artery during its systole to be one line, and
that the diameter of the same artery during its diastole is in health is
four lines, and in a fever with, great debility only two lines. It follows,
that the arterial fibres contract in health from a circle of twelve lines
in circumference to a circle of three lines in circumference, that is they
move through a space of nine lines in length. While the arterial fibres in
the fever with debility would twice contract from a circle of six lines to
a circle of three lines; that is while they move through a space equal to
six lines. Hence though the frequency of pulsation in fever be greater as
two to one, yet the velocity of contraction in health is greater as nine to
six, or as three to two.

On the contrary in inflammatory diseases with strength, as in the pleurisy,
the velocity of the contracting sides of the arteries is much greater than
in health, for if we suppose the number of pulsations in a pleurisy to be
half as much more than in health, that is as one hundred and twenty to
eighty, (which is about what generally happens in inflammatory diseases)
and if the diameter of the artery in diastole be one third greater than in
health, which I believe is near the truth, the result will be, that the
velocity of the contractile sides of the arteries will be in a pleurisy as
two and a half to one, compared to the velocity of their contraction in a
state of health, for if the circumference of the systole of the artery be
three lines, and the diastole in health be twelve lines in circumference,
and in a pleurisy eighteen lines; and secondly, if the artery pulsates
thrice in the diseased state for twice in the healthy one, it follows, that
the velocity of contraction in the diseased state to that in the healthy
state will be forty-five to eighteen, or as two and a half to one.

From hence it would appear, that if we had a criterion to determine the
velocity of the arterial contractions, it would at the same time give us
their strength, and thus be of more service in distinguishing diseases,
than the knowledge of their frequency. As such a criterion cannot be had,
the frequency of pulsation, the age of the patient being allowed for, will
in some measure assist us to distinguish arterial strength from arterial
debility, since in inflammatory diseases with strength the frequency seldom
exceeds one hundred and eighteen or one hu