ation of the motions of these glands with other motions, or
sensations, as by an extraneous body in the ear; of which I have known an
instance; or by the application of stizolobium, siliqua hirsuta, cowhage,
to the seat of the parotis, as some writers have affirmed.

II. 1. The lacrymal gland drinks up a certain fluid from the circumfluent
blood, and pours it on the ball of the eye, on the upper part of the
external corner of the eyelids. Though it may perhaps be stimulated into
the performance of its natural action by the blood, which surrounds its
origin, or by some part of that heterogeneous fluid; yet as the tears
secreted by this gland are more wanted at some times than at others, its
secretion is variable, like that of the saliva above mentioned, and is
chiefly produced when its excretory duct is stimulated; for in our common
sleep there seems to be little or no secretion of tears; though they are
occasionally produced by our sensations in dreams.

Thus when any extraneous material on the eye-ball, or the dryness of the
external covering of it, or the coldness of the air, or the acrimony of
some vapours, as of onions, stimulates the excretory duct of the lacrymal
gland, it discharges its contents upon the ball; a quicker secretion takes
place in the gland, and abundant tears succeed, to moisten, clean, and
lubricate the eye. These by frequent nictitation are diffused over the
whole ball, and as the external angle of the eye in winking is closed
sooner than the internal angle, the tears are gradually driven forwards,
and downwards from the lacrymal gland to the puncta lacrymalia.

2. The lacrymal sack, with its puncta lacrymalia, and its nasal duct, is a
complete gland; and is singular in this respect, that it neither derives
its fluid from, nor disgorges it into the circulation. The simplicity of
the structure of this gland, and both the extremities of it being on the
surface of the body, makes it well worthy our minuter observation; as the
actions of more intricate and concealed glands may be better understood
from their analogy to this.

3. This simple gland consists of two absorbing mouths, a belly, and an
excretory duct. As the tears are brought to the internal angle of the eye,
these two mouths drink them up, being stimulated into action by this fluid,
which they absorb. The belly of the gland, or lacrymal sack, is thus
filled, in which the saline part of the tears is absorbed, and when the
other end of the