Cuap. VI. DIGESTION. 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 (,'5 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 Novem- 
ber; 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 con- 
verted into minute spheres, surrounded by trans- 
parent, 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 un- 
equally corroded by the secretion. I need hardly 
8 
