stools,
which they blacken. The Iron meets intestinally with sulphuretted
hydrogen generated by fermenting excrementitious matters, and a black
sulphide of iron is formed. In this latter case, just as in the former,
some salutary influence which materially is inappreciable must be
wrought by the Iron on the blood-making organs, and functions. That
such Iron proves powerfully astringent when employed by either of these
methods cannot be denied ; also that it will promote the increased
production of red blood-corpuscles ; though by what exact process is
not known : most probably by some occult energy affecting the bodily
part with which the metal (infinitesimally volatilised) comes into
contact, whether when taken medicinally into the body, or when applied
as a compound mineral to its outside. Iron was administered for
curative purposes several centuries before Pliny's time. In this
country Sydenham was the first (1665) to point out these very important
therapeutic properties of Iron as a blood-making power. " To the
worn-out, and languid blood," said he, " it gives a spur or fillip,
whereby the animal spirits, which before lay prostrate, or sunk under
their own weight, are roused, and excited." Regarding Zinc: if a piece
of silver wire, (or a silver probe) be introduced high up into one of
the nostrils, and have its lower end brought into contact with a small
strip of Zinc plate, placed under the tongue, then a sensation not
unlike that of a strong flash of light will be produced in the eye on
the same side. Or, a similar perception, as though of some pungent taste, will
be produced at the moment of contact between the two said metals, if
one be inserted high up between the upper lip and its gum, whilst the
other is applied in like manner between the lower lip, and the lower
gum, or
