14 Dr. Young’s Lecture on the Functions 
more than two hundred pounds, in the state of the greatest 
possible action. 
The force, here assigned to each pulsation, agrees extremely 
well with the inference that may be drawn from an experi- 
ment of Hales, on the ascent of the blood in a tube connected 
with an artery of a horse. The whole height of the column 
being nine feet, the blood rose about three inches higher 
during each pulsation, which was repeated fifty or sixty times 
in a minute : now we may suppose the acceleration to have ex- 
tended a little beyond the first half of the space thus described, 
so that two inches were described in two fifths of a second ; and 
if there had been no friction, nor any other cause of retarda- 
tion, there can be no doubt that at least four inches would 
have been described in the same time ; but the same column 
of nine feet, if it had been actuated by its own weight, would 
have described thirty one inches in the same time : conse- 
quently the force with which the blood was forced through 
the artery was nearly one eighth of the whole force of ten- 
sion, as it appears in the former calculation. 
The magnitude of the pulse must diminish in the smaller 
arteries in the subduplicate proportion of the increase of the 
joint areas, in the same manner as the intensity of sound is 
shewn to decrease in diverging from a centre, in the subdu- 
plicate ratio of the quantity of matter affected by its motion at 
the same time. For example, in the arteries of the tenth 
order, of which the diameter is one thirteenth of an inch, its 
magnitude must be only one third as great as in the aorta, 
that is, the greatest progressive velocity of the blood must be 
eight inches and a half in a second only, and the dilatation 
one fiftieth part only of the diameter. In the vessels of the 
