are relaxed under very different circumstances, namely, during an
intense blush, the lacrymal glands are sometimes affected in a like manner,
for the eyes become suffused with tears.

It is difficult to conjecture how many reflex actions have originated,
but, in relation to the present case of the affection of the lacrymal
glands through irritation of the surface of the eye, it may be worth
remarking that, as soon as some primordial form became semi-terrestrial
in its habits, and was liable to get particles of dust into its eyes,
if these were not washed out they would cause much irritation;
and on the principle of the radiation of nerve-force to adjoining
nerve-cells, the lacrymal glands would be stimulated to secretion.
As this would often recur, and as nerve-force readily passes along
accustomed channels, a slight irritation would ultimately suffice
to cause a free secretion of tears.


[21] Bergeon, as quoted in the `Journal of Anatomy
and Physiology,' Nov. 1871, p. 235.

[22] See, for instance, a case given by Sir Charles Bell,
`Philosophical Transactions,' 1823, p. 177.

As soon as by this, or by some other means, a reflex action
of this nature had been established and rendered easy,
other stimulants applied to the surface of the eye--such as a
cold wind, slow inflammatory action, or a blow on the eyelids--
would cause a copious secretion of tears, as we know to be the case.
The glands are also excited into action through the irritation
of adjoining parts. Thus when the nostrils are irritated by