permanently retained both by man and the lower animals. For instance,
full-grown cats, when feeling warm and comfortable, often retain the
habit of alternately protruding their fore-feet with extended toes,
which habit they practised for a definite purpose whilst sucking their
mothers.
Another and distinct cause has probably strengthened the habit of
frowning, whenever the mind is intent on any subject and encounters
some difficulty. Vision is the most important of all the senses, and
during primeval times the closest attention must have been incessantly:
directed towards distant objects for the sake of obtaining prey and
avoiding danger. I remember being struck, whilst travelling in parts of
South America, which were dangerous from the presence of Indians, how
incessantly, yet as it appeared unconsciously, the half-wild Gauchos
closely scanned the whole horizon. Now, when any one with no covering
on his head (as must have been aboriginally the case with mankind),
strives to the utmost to distinguish in broad daylight, and especially
if the sky is bright, a distant object, he almost invariably contracts
his brows to prevent the entrance of too much light; the lower eyelids,
cheeks, and upper lip being at the same time raised, so as to lessen
the orifice of the eyes. I have purposely asked several persons, young
and old, to look, under the above circumstances, at distant objects,
making them believe that I only wished to test the power of their
vision; and they all behaved in the manner just described. Some of
them, also, put their open, flat hands over their eyes to keep out the
excess of light. Gratiolet, after making some remarks to nearly the
same effect,[905] says, Ce sont la des attitudes de vision difficile.
He concludes that the muscles round the eyes contract partly for the
sake of excluding too much light (which appears to me the more
important end), and partly to prevent all rays striking the retina,
except those which come direct from the object that is scrutinized. Mr.
Bowman, whom I consulted on this point, thinks that the contraction of
the surrounding muscles may, in addition, partly sustain the
consensual movements of the two eyes, by giving a firmer support while
the globes are brought to binocular vision by their own proper
muscles.
As the effort of viewing with care under a bright light a distant
object is both difficult and irksome, and as this effort has been
habitually accompanied, during numberless generations, by the
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