and half-minim drops were given to four leaves; so that each received
about 1/480 of a grain (.135 mg.) of the jelly; and, of course, much
less of dry chondrin. This acted most powerfully, for after only 3 hrs.
30 m. all four leaves were strongly inflected. Three of them began to
re-expand after 24 hrs., and in 48 hrs. were completely open; but the
fourth had only partially re-expanded. All the liquefied chondrin was
by this time absorbed. Hence a solution of chondrin seems to act far
more quickly and energetically than pure gelatine or isinglass; but I
am assured by good authorities that it is most difficult, or
impossible, to know whether chondrin is pure, and if it contained any
albuminous compound, this would have produced the above effects.
Nevertheless, I have thought these facts worth giving, as there is so
much doubt on the nutritious value of gelatine; and Dr. Lauder Brunton
does not know of any experiments with respect to animals on the
relative value of gelatine and chondrin.
Milk. We have seen in the last chapter that milk acts most powerfully
on the leaves; but whether this is due to the contained casein or
albumen, I know not. Rather large drops of milk excite so much
secretion (which is very acid) that it sometimes trickles down [page
114] from the leaves, and this is likewise characteristic of chemically
prepared casein. Minute drops of milk, placed on leaves, were
coagulated in about ten minutes. Schiff denies* that the coagulation of
milk by gastric juice is exclusively due to the acid which is present,
but attributes it in part to the pepsin; and it seems doubtful whether
with Drosera the coagulation can be wholly due to the acid, as the
secretion does not commonly colour litmus paper until the tentacles
have become well inflected; whereas the coagulation commences, as we
have seen, in about ten minutes. Minute drops of skimmed milk were
placed on the discs of five leaves; and a large proportion of the
coagulated matter or curd was dissolved in 6 hrs. and still more
completely in 8 hrs. These leaves re-expanded after two days, and the
viscid fluid left on their discs was then carefully scraped off and
examined. It seemed at first sight as if all the casein had not been
dissolved, for a little matter was left which appeared of a whitish
colour by reflected light. But this matter, when examined under a high
power, and when compared with a minute drop of skimmed milk coagulated
by acetic acid, was seen to consist exclusively of oil-globules, more
or less aggregated together, with no trace of casein. As I was not
familiar with the microscopical appearance of milk, I asked Dr. Lauder
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