Syntonin.—­This substance, extracted from muscle, was kindly prepared for me by Dr. Moore.  Very differently from fibrin, it acts quickly and energetically.  Small portions placed on the discs of three leaves caused their tentacles and blades to be strongly inflected within 8 hrs.; but no further observations were made.  It is probably due to the presence of this substance that raw meat is too powerful a stimulant, often injuring or even killing the leaves.

Areolar Tissue.—­Small portions of this tissue from a sheep were placed on the discs of three leaves; these became moderately well inflected in 24 hrs., but began to re-expand after 48 hrs., and were fully re-expanded in 72 hrs., always reckoning from the time when the bits were first given.  This substance, therefore, like fibrin, excites the leaves for only a short time.  The residue left on the leaves, after they were fully re-expanded, was examined under a high power and found much altered, but, owing to the presence of a quantity of elastic tissue, which is never acted on, could hardly be said to be in a liquefied condition.

Some areolar tissue free from elastic tissue was next procured from the visceral cavity of a toad, and moderately sized, as well as very small, bits were placed on five leaves.  After 24 hrs. two of the bits [page 103] were completely liquefied; two others were rendered transparent, but not quite liquefied; whilst the fifth was but little affected.  Several glands on the three latter leaves were now moistened with a little saliva, which soon caused much inflection and secretion, with the result that in the course of 12 additional hrs. one leaf alone showed a remnant of undigested tissue.  On the discs of the four other leaves (to one of which a rather large bit had been given) nothing was left except some transparent viscid fluid.  I may add that some of this tissue included points of black pigment, and these were not at all affected.  As a control experiment, small portions of this tissue were left in water and on wet moss for the same length of time, and remained white and opaque.  From these facts it is clear that areolar tissue is easily and quickly digested by the secretion; but that it does not greatly excite the leaves.

Cartilage.—­Three cubes (1/20 of an inch or 1.27 mm.) of white, translucent, extremely tough cartilage were cut from the end of a slightly roasted leg-bone of a sheep.  These were placed on three leaves, borne by poor, small plants in my greenhouse during November; and it seemed in the highest degree improbable that so hard a substance would be digested under such unfavourable circumstances.  Nevertheless, after 48 hrs., the cubes were largely dissolved and converted into minute spheres, surrounded by transparent, very acid fluid.  Two of these spheres were completely softened to their centres; whilst the third still contained a very small irregularly shaped core of solid cartilage.  Their surfaces were seen under the microscope to be curiously marked by prominent ridges, showing that the cartilage had been unequally corroded by the secretion.  I need hardly [page 104] say that cubes of the same cartilage, kept in water for the same length of time, were not in the least affected.