upon the eye.
Whether administered in the form of the official lamella or by subcutaneous
injection, physostigmine causes a contraction of the pupil more marked than
in the case of any other known drug. That this action is a direct and not a
nervous one is shown by the fact that if the eye be suddenly shaded the
pupil will dilate a little, showing that the nerves which cause dilatation
are still competent after the administration of physostigmine. Besides the
_sphincter pupillae_, the fibres of the ciliary muscle are stimulated.
There is consequently spasm of accommodation, so that clear vision of
distant objects becomes impossible. The intra-ocular tension is markedly
lowered. This action, at first sight somewhat obscure, is due to the
extreme pupillary contraction which removes the mass of the iris from
pressing upon the spaces of Fontana, through which the intraocular fluids
normally make a very slow escape from the eye into its efferent lymphatics.

There is a marked antagonism in nearly all important particulars between
the actions of physostigmine and of atropine. The details of this
antagonism, as well as nearly all our knowledge of this valuable drug, we
owe to Sir Thomas Fraser, who introduced it into therapeutics.

The clinical uses of physostigmine are based upon the facts of its
pharmacology, as above detailed. It has been recommended in cases of
chronic constipation, and of want of tone in the muscular wall of the
urinary bladder. It has undoubtedly been of value in many cases of tetanus,
in which it must be given in maximal doses. (The tetanus antitoxin should
invariably be employed as well.) Sir Thomas Fraser differs from nearly all
other authorities in regarding the drug as useless in cases of strychnine
poisoning, and the question must be left open. There is some doubtful
evidence of the value of the alkaloid in chorea. The oculist uses it for at
least six purposes. Its stimulant action on the iris and ciliary muscle is
employed when they are weak or paralysed. It is used in all cases where one
needs to reduce the intra-ocular tension, and for this and other reasons in
glaucoma. It is naturally the most efficient agent in relieving the
discomfort or intolerable pain of photophobia; and it is the best means of
breaking down adhesions of the iris, and of preventing prolapse of the iris
after injuries to the cornea. In fact it is hardly possible to
over-estimate its value in ophthalmology. The drug has been