effects; whilst small doses of potassium salts cause death by suddenly
arresting the movements of the heart. An excellent instance of the
different action of the two series is presented by the phosphate of
soda quickly causing vigorous inflection, whilst phosphate of potash is
quite inefficient. The great power of the former is probably due to the
presence of phosphorus, as in the cases of phosphate of lime and of
ammonia. Hence we may infer that Drosera cannot obtain phosphorus from
the phosphate of potash. This is remarkable, as I hear from Dr. Burdon
Sanderson that phosphate of potash is certainly decomposed within the
bodies of animals. Most of the salts of soda act very rapidly; the
iodide acting slowest. The oxalate, nitrate, and citrate seem to have a
special tendency to cause the blade of the leaf to be inflected. The
glands of the disc, after absorbing the citrate, transmit hardly any
motor impulse to the outer tentacles; and in this character the citrate
of soda resembles the citrate of ammonia, or a decoction of
grass-leaves; these three fluids all acting chiefly on the blade.
It seems opposed to the rule of the preponderant influence of the base
that the nitrate of lithium causes moderately rapid inflection, whereas
the acetate causes none; but this metal is closely allied to sodium
[page 188] and potassium,* which act so differently; therefore we might
expect that its action would be intermediate. We see, also, that
caesium causes inflection, and rubidium does not; and these two metals
are allied to sodium and potassium. Most of the earthy salts are
inoperative. Two salts of calcium, four of magnesium, two of barium,
and two of strontium, did not cause any inflection, and thus follow the
rule of the preponderant power of the base. Of three salts of
aluminium, one did not act, a second showed a trace of action, and the
third acted slowly and doubtfully, so that their effects are nearly
alike.
Of the salts and acids of ordinary metals, seventeen were tried, and
only four, namely those of zinc, lead, manganese, and cobalt, failed to
cause inflection. The salts of cadmium, tin, antimony, and iron, act
slowly; and the three latter seem more or less poisonous. The salts of
silver, mercury, gold, copper, nickel, and platinum, chromic and
arsenious acids, cause great inflection with extreme quickness, and are
deadly poisons. It is surprising, judging from animals, that lead and
barium should not be poisonous. Most of the poisonous salts make the
glands black, but chloride of platinum made them very pale. I shall
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