s principally characteristic of viperine poisoning, and only very
exceptionally produced by the poison of colubrines. It is among the
symptoms of snakebite poisoning one of the most interesting ones, but
also one most difficult of explanation. There can be no doubt that it is
produced by vaso-motor paresis and paralysis. We further know that it is
preceded by dilatation of the capillaries and small veins, and that it
is effected principally through the process known as diapedesis, or the
passage of both red and white corpuscles with plasma through the
unruptured capillary membrane, and even the thin one of small veins,
which is nearly of the same structure, being composed of endothelial
cells united by cement. This membrane possesses a certain degree of
porosity, which is probably increased by dilatation. In the absence of
plain muscular fibres contraction and dilatation of the capillaries can
only be effected by a corresponding contraction and expansion of the
nuclei of the endothelial cells. As fibrils derived from non-medullated
nerves terminate in small end-butts in connection with the capillary
membrane, we may assume that the nuclei of the endothelial cells are
under the sway of vaso-motor nerve currents, that weak ones will expand,
strong ones contract them. We may further assume that the red and white
corpuscles force their way out of the vessels through pores in the
cement substance, since a passage of cell through cell is not thinkable.
Thus far we see our way fairly clear. But the question now arises: what
causes the solid constituents of the blood to force their way through
the capillary membranes all over the mucous surfaces, even the
conjunctiva, and not these alone, but also through serous membranes such
as the pericardium, and strangest of all, through old scars in the skin?
If the most modern ideas as to the cause of diapedesis being blood
pressure are correct, it is quite incomprehensible how it can take place
in the absence of blood pressure, and take place so extensively. The
theory of blood pressure may apply to diapedesis accompanying the
inflammatory process. In snakebite poisoning it is more likely to be due
to passive engorgement of the capillary system and probably also to
blockage of corpuscles in the finest capillary tubes. In vaso-motor
paresis, and still more paralysis, the arterioles supplying the
capillaries are widely dilated, and at the lowest blood pressure
probably send more blood into