swallow is formed of matter secreted by the salivary glands; two grains
were added to one ounce of distilled water (one part to 218), which was
boiled for several minutes, but did not dissolve the whole. The
usual-sized drops were placed on three leaves, and these in 1 hr. 30 m.
were well, and in 2 hrs. 15 m. closely, inflected.
Isinglass. Drops of a solution about as thick as milk, and of a still
thicker solution, were placed on eight leaves, and the tentacles of all
became inflected. In one case the exterior tentacles were well curved
in after 6 hrs. 30 m., and the blade of the leaf to a partial extent
after 24 hrs. As saliva acted so efficiently, and yet contains so small
a proportion of nitrogenous matter, I tried how small a quantity of
isinglass would act. One part was dissolved in 218 parts of distilled
water, and drops were placed on four leaves. After 5 hrs. two of these
were considerably and two moderately inflected; after 22 hrs. the
former were greatly and the latter much more inflected. In the course
of 48 hrs.
* Mucus from the air-passages is said in Marshall, Outlines of
Physiology, vol. ii. 1867, p. 364, to contain some albumen.
** Muller s Elements of Physiology, Eng. Trans. vol. i., p. 514.
[page 81]
from the time when the drops were placed on the leaves, all four had
almost re-expanded. They were then given little bits of meat, and these
acted more powerfully than the solution. One part of isinglass was next
dissolved in 437 of water; the fluid thus formed was so thin that it
could not be distinguished from pure water. The usual-sized drops were
placed on seven leaves, each of which thus received 1/960 of a grain
(.0295 mg.). Three of them were observed for 41 hrs., but were in no
way affected; the fourth and fifth had two or three of their exterior
tentacles inflected after 18 hrs.; the sixth had a few more; and the
seventh had in addition the edge of the leaf just perceptibly curved
inwards. The tentacles of the four latter leaves began to re-expand
after an additional interval of only 8 hrs. Hence the 1/960 of a grain
of isinglass is sufficient to affect very slightly the more sensitive
or active leaves. On one of the leaves, which had not been acted on by
71