The greatest exertion of the muscles of the body, if those of the chest
are not brought into strong action in expelling or compressing the air
within the lungs, does not lead to the contraction of the muscles round
the eyes. I have observed my sons using great force in gymnastic
exercises, as in repeatedly raising their suspended bodies by their
arms alone, and in lifting heavy weights from the ground, but there was
hardly any trace of contraction in the muscles round the eyes.
As the contraction of these muscles for the protection of the eyes
during violent expiration is indirectly, as we shall hereafter see, a
fundamental element in several of our most important expressions, I was
extremely anxious to ascertain how far Sir C. Bell s view could be
substantiated. Professor Donders, of Utrecht,[614] well known as one of
the highest authorities in Europe on vision and on the structure of the
eye, has most kindly undertaken for me this investigation with the aid
of the many ingenious mechanisms of modern science, and has published
the results.[615] He shows that during violent expiration the external,
the intra-ocular, and the retro-ocular vessels of the eye are all
affected in two ways, namely by the increased pressure of the blood in
the arteries, and by the return of the blood in the veins being
impeded. It is, therefore, certain that both the arteries and the veins
of the eye are more or less distended during violent expiration. The
evidence in detail may be found in Professor Donders valuable memoir.
We see the effects on the veins of the head, in their prominence, and
in the purple colour of the face of a man who coughs violently from
being half choked. I may mention, on the same authority, that the whole
eye certainly advances a little during each violent expiration. This is
due to the dilatation of the retro-ocular vessels, and might have been
expected from the intimate connection of the eye and brain; the brain
being known to rise and fall with each respiration, when a portion of
the skull has been removed; and as may be seen along the unclosed
sutures of infants heads. This also, I presume, is the reason that the
eyes of a strangled man appear as if they were starting from their
sockets.
With respect to the protection of the eye during violent expiratory
efforts by the pressure of the eyelids, Professor Donders concludes
from his various observations that this action certainly limits or
entirely removes the dilatation of the vessels.[616] At such times, he
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