pungent vapours, though the eyelids may be kept firmly closed,
tears are copiously secreted; and this likewise follows from
a blow on the nose, for instance from a boxing-glove. A stinging
switch on the face produces, as I have seen, the same effect.
In these latter cases the secretion of tears is an incidental result,
and of no direct service. As all these parts of the face,
including the lacrymal glands, are supplied with branches
of the same nerve, namely, the fifth, it is in some degree
intelligible that the effects of the excitement of any one branch
should spread to the nerve-cells or roots of the other branches.

The internal parts of the eye likewise act, under certain conditions,
in a reflex manner on the lacrymal glands. The following statements
have been kindly communicated to me by Mr. Bowman; but the subject
is a very intricate one, as all the parts of the eye are so intimately
related together, and are so sensitive to various stimulants.
A strong light acting on the retina, when in a normal condition,
has very little tendency to cause lacrymation; but with unhealthy
children having small, old-standing ulcers on the cornea, the retina
becomes excessively sensitive to light, and exposure even to common
daylight causes forcible and sustained closure of the lids,
and a profuse flow of tears. When persons who ought to begin
the use of convex glasses habitually strain the waning power
of accommodation, an undue secretion of tears very often follows,
and the retina is liable to become unduly sensitive to light.
In general, morbid affections of the surface of the eye,
and of the ciliary structures concerned in the accommodative act,
are prone to be accompanied with excessive secretion of tears.
Hardness of the eyeball, not rising to inflammation, but implying
a want of balance between the fluids poured out and again taken up by