of the globules being distinctly seen. In the veins,
a single globule, or a number of globules, may be
readily and distinctly traced in their motion along
their varied course.
In the arteries, a pulsatory or accelerated movement
of the blood is seen quite distinctly,—so
distinctly indeed as to enable the observer to
number the heart’s beat with the utmost facility
and accuracy. This pulsatory movement is not,
in the unimpeded circulation, extended to the
blood in the capillaries or veins. By a peculiar
anatomy, which will he described shortly, the flow
of the blood is made uniform at the very commencement
of the former series of vessels.
In no instance have I been able to detect an
anastomosis between the minute arteries. Such
anastomoses between the roots of the veins are,
however, not uncommon ; and then a singular and
interesting phenomenon is usually observed. The
anastomosing roots which unite the two veins,
present the curious fact of a double and contrary
course in the flow of the blood: from some point
or space, at which they are joined by one or more
capillary vessels, the globules of blood are seen
flowing in opposite directions into each of the
two veins. If it be a point, there is an appearance
of more crowded globules moving slightly in the
form of a vortex ; if a space, the globules move
variously in it, and sometimes appear stagnant for
a moment. It is also interesting to observe that,
by the motions of the animal, or other causes
which disturb the circulation, the globules of
blood frequently pursue one course only in this
anastomosing vessel ; and this effect is permanent,
if one of the veins with which it communicates;
he permanently obstructed by a ligature or other
means ; that vein then presents the singular phenomena
of giving off branches instead of receiving
roots of smaller vessels, and of a retrograde
course in the flow of the globules of blood. The
anastomoses between the capillary vessels are
exceedingly frequent indeed. The final object of
this difference in the character of the arterial and
venous branches and roots is very obvious. The
circulation in the arteries is forcible and rapid,
and not easily interrupted; anastomoses are not
therefore required : the circulation in the veins,
on the contrary, is slower and feebler, and far
more easily suppressed by pressure or other accidents
; if there were no anastomoses, the blood