of some other salts, to 437 of water, excites the glands to largely
increased secretion; on the other hand, tartrate of antimony produces
no such effect. Immersion in many acids (of the strength of one part
to 437 of water) likewise causes a wonderful amount of [page 14]
secretion, so that when the leaves are lifted out, long ropes of
extremely viscid fluid hang from them. Some acids, on the other hand,
do not act in this manner. Increased secretion is not necessarily
dependent on the inflection of the tentacle, for particles of sugar and
of sulphate of zinc cause no movement.

It is a much more remarkable fact that when an object, such as a bit of
meat or an insect, is placed on the disc of a leaf, as soon as the
surrounding tentacles become considerably inflected, their glands pour
forth an increased amount of secretion. I ascertained this by selecting
leaves with equal-sized drops on the two sides, and by placing bits of
meat on one side of the disc; and as soon as the tentacles on this side
became much inflected, but before the glands touched the meat, the
drops of secretion became larger. This was repeatedly observed, but a
record was kept of only thirteen cases, in nine of which increased
secretion was plainly observed; the four failures being due either to
the leaves being rather torpid, or to the bits of meat being too small
to cause much inflection. We must therefore conclude that the central
glands, when strongly excited, transmit some influence to the glands of
the circumferential tentacles, causing them to secrete more copiously.

It is a still more important fact (as we shall see more fully when we
treat of the digestive power of the secretion) that when the tentacles
become inflected, owing to the central glands having been stimulated
mechanically, or by contact with animal matter, the secretion not only
increases in quantity, but changes its nature and becomes acid; and