ble juices._

There are besides some motions of the sap in vegetables, which bear analogy
to our present subject; and as the vegetable tribes are by many
philosophers held to be inferior animals, it may be a matter of curiosity
at least to observe, that their absorbent vessels seem evidently, at times,
to be capable of a retrograde motion. Mr. Perault cut off a forked branch
of a tree, with the leaves on; and inverting one of the forks into a vessel
of water, observed, that the leaves on the other branch continued green
much longer than those of a similar branch, cut off from the same tree;
which shews, that the water from the vessel was carried up one part of the
forked branch, by the retrograde motion of its vessels, and supplied
nutriment some time to the other part of the branch, which was out of the
water. And the celebrated Dr. Hales found, by numerous very accurate
experiments, that the sap of trees rose upwards during the warmer hours of
the day, and in part descended again during the cooler ones. Vegetable
Statics.

It is well known that the branches of willows, and of many other trees,
will either take root in the earth or engraft on other trees, so as to have
their natural direction inverted, and yet flourish with vigour.

Dr. Hope has also made this pleasing experiment, after the manner of
Hales--he has placed a forked branch, cut from one tree, erect between two
others; then cutting off a part of the bark from one fork applied it to a
similar branch of one of the trees in its vicinity; and the same of the
other fork; so that a tree is seen to grow suspended in the air, between
two other trees; which supply their softer friend with due nourishment.

Miranturque novas frondes, et non sua poma.

All these experiments clearly evince, that the juices of vegetables can
occasionally pass either upwards or downwards in their absorbent system of
vessels.

X. _Objections answered._

The following experiment, at first view, would seem to invalidate this
opinion of the retrograde motions of the lymphatic vessels, in some
diseases.

About a gallon of milk having been giving to an hungry swine, he was
suffered to live about an hour, and was then killed by a stroke or two on
his head with an axe.--On opening his belly the lacteals were well seen
filled with chyle; on irritating many of the branches of them with a knife,
they did not appear to empty themselves hastily; but they did however carry
forwards their c