98 ANALYTIC SECT. XI. 
as capillary attraction, must draw the liquid into 
its cavity; and contraction of it forward the fluid 
along its canal. Such is the relation of the veins. 
with the blood in the capillaries; the expansion of 
the veins sucks the blood from the capillaries, and 
their contraction propels it in the direction of the 
heart, as being the least resisting course. 
ccxxvil. But the irritability of the veins is not 
the only cause of motion in their tubes; the 
impetus of the heart is not wholly expended ‘on 
the arteries; for a pulsation, synchronous with 
that of the heart, has been, though very rarely, 
observed in the veins. A case of this kind is 
recorded by Dr. Parry, of Bath. 
ccexxvill. The mechanism of the venal event 
admirably contrived to secure any counter motion 
of the blood im the veins, admitting its free pas- 
sage in the direction of the heart, and effectually 
opposing its reflux. 
ccxxix. As the right auricle pumps up the blood 
from the venz cave, the pressure of the atmo- 
sphere upon the surface of the body, must contri- 
bute to the progressive motion of the blood from 
the small veins to the great venous trunks. 
coxxx. The old anatomists knew of no absorp- 
tion but by the venous system. John Hunter denied 
the absorbent power of the veins; but. this 
opinion, which was, in fact, incompatible’ with 
the irritability of these tubes, has recently been 
