[ 32 + 3 
Such was Boerhaave’s doCtrine concerning the vaf- 
cuiar fyftem of animal bodies ; like many of his- 
other notions, ingenious, plaufible, and recommend- 
ing itfelf, at firft light, by an appearance of geome- 
trical and mechanical accuracy : but founded upon 
inefficient data, and by no means to be reconciled 
to appearances. 
For, in the firft place, fhould we admit his hypo- 
thefts, it is certain, that the conical or converging 
form of the aorta, and the change of direction in its^ 
branches, muft, in the diftant blood-veftels, occafton 
a great reftftance to the moving blood, and a great 
diminution of its velocity. Suppofe that this refift- 
ance be, in any capillary red artery, to the reftftance 
in the trunk of the aorta, as any larger affignable num- 
ber is to unit : the reftftance, then, in a capillary ferous- 
artery will, to that in the aorta, be as the fquare of 
that number is to unit ; in the capillary lymphatic, 
as the cube ; and fo in progreffion : that is, the ve- 
locity of the fluids, in the remoter l'eries of veffels,. 
will be, phyficially, nothing. But we know, on the 
contrary, that fome very remote feries of veffels have 
their contents moved with a very confiderable velo- 
city ; particularly the veffels of the infenftble per- 
fpiration r and in anatomical injections, the liquor 
thrown into an artery fcarce returns more eafily or 
fpeedily by the eorrefponding vein, than by the moft 
fubtile excretory duCts. Moreover, there are an in- 
finite number of obfervations of morbid cafes, in 
which the red blood itfelf has been evacuated thro’ 
fome of the moft remote feries of veffels, merely 
from an occaftonal temporary obftruCtion in one part, 
or a praeter natural laxity in another ; and without 
any 
