which in 24 hrs. became fairly well marked. After four days two of the
leaves began to open, and the other two were then almost fully
re-expanded. It is therefore clear that this chlorophyll contained
matter which excited the leaves to a moderate degree; but judging by
the eye, little or none was dissolved; so that in a pure state it would
not probably have been attacked by the secretion. Dr. Sanderson tried
that which I [page 126] used, as well as some freshly prepared, with
artificial digestive liquid, and found that it was not digested. Dr.
Lauder Brunton likewise tried some prepared by the process given in the
British Pharmacopoeia, and exposed it for five days at the temperature
of 37 Cent. to digestive liquid, but it was not diminished in bulk,
though the fluid acquired a slightly brown colour. It was also tried
with the glycerine extract of pancreas with a negative result. Nor does
chlorophyll seem affected by the intestinal secretions of various
animals, judging by the colour of their excrement.
It must not be supposed from these facts that the grains of
chlorophyll, as they exist in living plants, cannot be attacked by the
secretion; for these grains consist of protoplasm merely coloured by
chlorophyll. My son Francis placed a thin slice of spinach leaf,
moistened with saliva, on a leaf of Drosera, and other slices on damp
cotton-wool, all exposed to the same temperature. After 19 hrs. the
slice on the leaf of Drosera was bathed in much secretion from the
inflected tentacles, and was now examined under the microscope. No
perfect grains of chlorophyll could be distinguished; some were
shrunken, of a yellowish-green colour, and collected in the middle of
the cells; others were disintegrated and formed a yellowish mass,
likewise in the middle of the cells. On the other hand, in the slices
surrounded by damp cotton-wool, the grains of chlorophyll were green
and as perfect as ever. My son also placed some slices in artificial
gastric juice, and these were acted on in nearly the same manner as by
the secretion. We have seen that bits of fresh cabbage and spinach
leaves cause the tentacles to be inflected and the glands to pour forth
much acid secretion; and there can be little doubt that it is the
protoplasm forming the grains of chlorophyll, as well as that lining
the walls of the cells, which excites the leaves.
Fat and Oil. Cubes of almost pure uncooked fat, placed on several
leaves, did not have their angles in the least rounded. We have also
seen that the oil-globules in milk are not digested. Nor does olive oil
110