ollow up the interesting research, and take two
frogs. Under the skin of one of them we inject a few drops of the poison
solution, the other one for comparison we leave intact, and place both
into a glass globe partly filled with water. In a very short time we
have no difficulty to identify the poisoned frog. Its hind legs begin to
drop and their movements become sluggish. This difficulty increases from
minute to minute, until at last all motion ceases, and the legs hang
down completely paralysed. At the same time we observe that the animal
shows increasing difficulty of breathing, that, even when taken out of
the water, and placed on the table before us it gasps for breath and is
unable to move. At last respiration ceases altogether and the frog dies.

Two problems now present themselves for solution. In the first place we
have to account for the fact of the snake-poison leaving the lower forms
of animal life intact and being fatal to the higher ones. The symptoms
we have observed in the frog point unmistakably to an affection of the
nervous system as their cause. Now we know that the lower forms which
the poison does not affect have no such system, and we are justified to
infer that to the absence of this system they owe their immunity. This
inference leads us on to a second one equally justifiable, namely, that
there is a certain unaccountable attraction between the delicate nerve
tissue and the subtle ophidian poison, which renders the latter a
specific nerve poison.

Our second problem is to ascertain the nature of the change in the
nerves, to find out, if possible, whether it is merely functional or an
actual interference with the structure of either cells or fibres. With
this end in view we once more consult the microscope. We make two
preparations, one of nerve fibres and of nerve cells of the poisoned
frog, and, under the microscope, compare them carefully with an
analogous one from the killed healthy frog. The result is purely
negative as regards structural change. Both present identical and
perfectly normal pictures of apparently healthy cells and fibres. There
being no visible structural change we are driven to the conclusion that
only a functional one has been effected by the poison, and with the
symptoms observed all pointing in that direction, that it is of central
origin.

The writer's theory as to the action of snake-poison, formed, in the
first instance from observations made at the bedside of his pa