flaccid. Placed in pure water, next day evidently dead. A rapid poison.
Nickel, Chloride of. Three leaves immersed in ninety minims of a
solution of one part to 437 of water; in 25 m. considerable inflection,
and in 3 hrs. all the tentacles closely inflected. After 22 hrs. still
closely inflected; most of the glands, but not all, blackened. The
leaves were then placed in water; after 24 hrs. remained inflected;
were somewhat discoloured, with the glands and tentacles dingy red.
Probably killed.
Cobalt, Chloride of. Three leaves immersed in ninety minims of a
solution of one part to 437 of water; after 23 hrs. there was not a
trace of inflection, and the glands were not more blackened than often
occurs after an equally long immersion in water.
Platinum, Chloride of. Three leaves immersed in ninety minims of a
solution of one part to 437 of water; in 6 m. some inflection, which
became immense after 48 m. After 3 hrs. the glands were rather pale.
After 24 hrs. all the tentacles still closely inflected; glands
colourless; remained in same state for four days; leaves evidently
killed.]
Concluding Remarks on the Action of the foregoing Salts. Of the
fifty-one salts and metallic acids which were tried, twenty-five caused
the tentacles to be inflected, and twenty-six had no such effect, two
rather doubtful cases occurring in each series. In the table at the
head of this discussion, the salts are arranged according to their
chemical affinities; but their action on Drosera does not seem to be
thus governed. The nature of the base is far more important, as far as
can be judged from the few experiments here given, than that of the
acid; and this is the conclusion at which physiologists have arrived
with respect to animals. We see this fact illustrated in all the nine
salts of soda causing inflection, and in not being poisonous except
when given in large doses; whereas seven of [page 187] the
corresponding salts of potash do not cause inflection, and some of them
are poisonous. Two of them, however, viz. the oxalate and iodide of
potash, slowly induced a slight and rather doubtful amount of
inflection. This difference between the two series is interesting, as
Dr. Burdon Sanderson informs me that sodium salts may be introduced in
large doses into the circulation of mammals without any injurious
168