Fibrin.—­Bits of fibrin were left in water during four days, whilst the following experiments were tried, but they were not in the least acted on.  The fibrin which I first used was not pure, and included dark particles:  it had either not been well prepared or had subsequently undergone some change.  Thin portions, about 1/10 of an inch square, were placed on several leaves, and though the fibrin was soon liquefied, the whole was never dissolved.  Smaller particles were then placed on four leaves, and minute [page 101] drops of hydrochloric acid (one part to 437 of water) were added; this seemed to hasten the process of digestion, for on one leaf all was liquified and absorbed after 20 hrs.; but on the three other leaves some undissolved residue was left after 48 hrs.  It is remarkable that in all the above and following experiments, as well as when much larger bits of fibrin were used, the leaves were very little excited; and it was sometimes necessary to add a little saliva to induce complete inflection.  The leaves, moreover, began to re-expand after only 48 hrs., whereas they would have remained inflected for a much longer time had insects, meat, cartilage, albumen, &c., been placed on them.

I then tried some pure white fibrin, sent me by Dr. Burdon Sanderson.

[Experiment 1.—­Two particles, barely 1/20 of an inch (1.27 mm.) square, were placed on opposite sides of the same leaf.  One of these did not excite the surrounding tentacles, and the gland on which it rested soon dried.  The other particle caused a few of the short adjoining tentacles to be inflected, the more distant ones not being affected.  After 24 hrs. both were almost, and after 72 hrs. completely, dissolved.

Experiment 2.—­The same experiment with the same result, only one of the two bits of fibrin exciting the short surrounding tentacles.  This bit was so slowly acted on that after a day I pushed it on to some fresh glands.  In three days from the time when it was first placed on the leaf it was completely dissolved.

Experiment 3.—­Bits of fibrin of about the same size as before were placed on the discs of two leaves; these caused very little inflection in 23 hrs., but after 48 hrs. both were well clasped by the surrounding short tentacles, and after an additional 24 hrs. were completely dissolved.  On the disc of one of these leaves much clear acid fluid was left.

Experiment 4.—­Similar bits of fibrin were placed on the discs of two leaves; as after 2 hrs. the glands seemed rather dry, they were freely moistened with saliva; this soon caused strong inflection both of the tentacles and blades, with copious [page 102] secretion from the glands.  In 18 hrs. the fibrin was completely liquefied, but undigested atoms still floated in the liquid; these, however, disappeared in under two additional days.]

From these experiments it is clear that the secretion completely dissolves pure fibrin.  The rate of dissolution is rather slow; but this depends merely on this substance not exciting the leaves sufficiently, so that only the immediately adjoining tentacles are inflected, and the supply of secretion is small.