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
this occurs before the glands have touched the object on the centre of
the leaf. This acid is of a different nature from that contained in the
tissue of the leaves. As long as the [page 15] tentacles remain closely
inflected, the glands continue to secrete, and the secretion is acid;
so that, if neutralised by carbonate of soda, it again becomes acid
after a few hours. I have observed the same leaf with the tentacles
closely inflected over rather indigestible substances, such as
chemically prepared casein, pouring forth acid secretion for eight
successive days, and over bits of bone for ten successive days.
The secretion seems to possess, like the gastric juice of the higher
animals, some antiseptic power. During very warm weather I placed close
together two equal-sized bits of raw meat, one on a leaf of the
Drosera, and the other surrounded by wet moss. They were thus left for
48 hrs., and then examined. The bit on the moss swarmed with infusoria,
and was so much decayed that the transverse striae on the muscular
fibres could no longer be clearly distinguished; whilst the bit on the
leaf, which was bathed by the secretion, was free from infusoria, and
its striae were perfectly distinct in the central and undissolved
portion. In like manner small cubes of albumen and cheese placed on wet
moss became threaded with filaments of mould, and had their surfaces
slightly discoloured and disintegrated; whilst those on the leaves of
Drosera remained clean, the albumen being changed into transparent
fluid.
As soon as tentacles, which have remained closely inflected during
17