be investigated and established. In the ensuing
winters of 1833, 4, and 5, I gave much attention to the subject, and
employed professors in my school in the departments of chemistry and
natural philosophy, who assisted me,--particularly by their ingenuity in
the construction of such simple pieces of apparatus as were needed.

Thus we proved that, although the heart's action gives pulsation, it
does not necessarily give circulation. By an endless india-rubber tube,
filled with water, coiled upon a table and struck repeatedly at one
point, a pulsation was produced throughout, but no circulation. By
affixing the tube to a vessel of water, and laying it on an inclined
plane, the water ran through it in an equable current, making
circulation with pulsation. Clasping the hand upon the tube in
successive contractions, the fluid passed on _per saltem_, producing
circulation and pulsation united, but no acceleration of the current.
Now, add valves to the tube on each side of the opening hand, and you
will have the current--which is moving by gravitation, accelerated by
the hand's impulse, as the blood's current, first moved by respiration,
undoubtedly is by the heart's beat.

The heart we regard as the grand regulator of the blood's flow; and it
is admirably situated for measuring out a regular portion of blood at
every contraction. John Bell, believing in the Harveian theory, said,
"It is awful to think of the unfixed position of the heart;" and
Dr. Arnott declared that "the heart, the heart alone, is the ragged
anomaly in the laws of fitness in mechanics." The heart was now seen to
have a right position; for it should swing loose that its moorings be
not endangered; and, as whatever impugns the Creator's unerring wisdom
must be wrong, so the presumption is, that whatever vindicates it must
be right.

My hypothesis assumed the principle, that, if an endless hollow tube be
filled with a liquid, the liquid can be made to circulate perpetually,
if it be heated at one point and cooled before its return. A drawing of
the simple apparatus by which this problem was proved, is given in my
published work on "the Motive Powers, &c." The figure which represents
this apparatus gives the learner the most simple idea possible of the
connection of the respiratory and circulatory systems, and of the
combination of the two motive powers; the first, or chemical, coming
from the lungs, and the second, or mechanical, from the heart.

Suppose t