(1) Flies were placed on many leaves, and excited the glands to secrete
copiously; the secretion always becoming acid, though not so before.
After a time these insects were rendered so tender that their limbs and
bodies could be separated by a mere touch, owing no doubt to the
digestion and disintegration of their muscles. The glands in contact
with a small fly continued to secrete for four days, and then became
almost dry. A narrow strip of this leaf was cut off, and the glands of
the longer and shorter hairs, which had lain in contact for the four
days with the fly, and those which had not touched it, were compared
under the microscope and presented a wonderful contrast. Those which
had been in contact were filled with brownish granular matter, the
others with homogeneous fluid. There could therefore be no doubt that
the former had absorbed matter from the fly.
(2) Small bits of roast meat, placed on a leaf, always caused much acid
secretion in the course of a few hours—in one case within 40 m. When
thin fibres of meat were laid along the margin of a leaf which stood
almost upright, the secretion ran down to the ground. Angular bits of
meat, placed in little pools of the secretion near the margin, were in
the course of
* ‘English Botany,’ by Sir J.E. Smith; with coloured figures by J.
Sowerby; edit. of 1832, tab. 24, 25, 26. [page 382]
two or three days much reduced in size, rounded, rendered more or less
colourless and transparent, and so much softened that they fell to
pieces on the slightest touch. In only one instance was a very minute
particle completely dissolved, and this occurred within 48 hrs. When
only a small amount of secretion was excited, this was generally
absorbed in from 24 hrs. to 48 hrs.; the glands being left dry. But
when the supply of secretion was copious, round either a single rather
large bit of meat, or round several small bits, the glands did not
become dry until six or seven days had elapsed. The most rapid case of
absorption observed by me was when a small drop of an infusion of raw
meat was placed on a leaf, for the glands here became almost dry in 3
hrs. 20 m. Glands excited by small particles of meat, and which have
quickly absorbed their own secretion, begin to secrete again in the
course of seven or eight days from the time when the meat was given
them.
(3) Three minute cubes of tough cartilage from the leg-bone of a sheep
were laid on a leaf. After 10 hrs. 30 m. some acid secretion was
excited, but the cartilage appeared little or not at all affected.
After 24 hrs. the cubes were rounded and much reduced in size; after 32
hrs. they were softened to the centre, and one was quite liquefied;
after 35 hrs. mere traces of solid cartilage were left; and after 48
hrs. a trace could still be seen through a lens in only one of the
three. After 82 hrs. not only were all three cubes completely
liquefied, but all the secretion was absorbed and the glands left dry.
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