[12] `The Anatomy of Expression,' 1844, p. 106. See also his paper
in the `Philosophical Transactions,' 1822, p. 284, ibid. 1823, pp.
166 and 289. Also `The Nervous System of the Human Body,' 3rd edit.
1836, p. 175.

Not only are the muscles round the eyes strongly contracted, as Sir C. Bell
states and as I have often observed, during screaming, loud laughter,
coughing, and sneezing, but during several other analogous actions.
A man contracts these muscles when he violently blows his nose.
I asked one of my boys to shout as loudly as he possibly could,
and as soon as he began, he firmly contracted his orbicular muscles;
I observed this repeatedly, and on asking him why he had every time
so firmly closed his eyes, I found that he was quite unaware of the fact:
he had acted instinctively or unconsciously.

It is not necessary, in order to lead to the contraction of
these muscles, that air should actually be expelled from the chest;
it suffices that the muscles of the chest and abdomen should contract
with great force, whilst by the closure of the glottis no air escapes.
In violent vomiting or retching the diaphragm is made to descend
by the chest being filled with air; it is then held in this position
by the closure of the glottis, "as well as by the contraction of its own
fibres."[13] The abdominal muscles now contract strongly upon the stomach,
its proper muscles likewise contracting, and the contents are thus ejected.
During each effort of vomiting "the head becomes greatly congested,
so that the features are red and swollen, and the large veins of
the face and temples visibly dilated." At the same time, as I know
from observation, the muscles round the eyes are strongly contracted.
This is likewise the case when the abdominal muscles act downwards
with unusual force in expelling the contents of the intestinal canal.