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,[5] 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 contraction of the eyebrows, the habit of frowning will thus have been much strengthened; although it was originally practised during infancy from a quite independent cause, namely as the first step in the protection of the eyes during screaming. There is, indeed, much analogy, as far as the state of the mind is concerned, between intently scrutinizing a distant object, and following out an obscure train of thought, or performing some little and troublesome mechanical work. The belief that the habit of contracting the brows is continued when there is no need whatever to exclude too much light, receives support from the cases formerly alluded to, in which the eyebrows or eyelids are acted on under certain circumstances in a useless manner, from having been similarly used, under analogous circumstances, for a serviceable purpose. For instance, we voluntarily close our eyes when we do not wish to see any object, and we are apt to close them, when we reject a proposition, as if we could not or would not see it; or when we think about something horrible. We raise our eyebrows when we wish to see quickly all round us, and we often do the same, when we earnestly desire to remember something; acting as if we endeavoured to see it.

[5] `De la Physionomie,' pp. 15, 144, 146. Mr. Herbert Spencer accounts for frowning exclusively by the habit of contracting the brows as a shade to the eyes in a bright light: see `Principles of Physiology,' 2nd edit. 1872, p. 546.

_Abstraction. Meditation_.--When a person is lost in thought with his mind absent, or, as it is sometimes said, "when he is in a brown study," he does not frown, but his eyes appear vacant. The lower eyelids are generally raised and wrinkled, in the same manner as when a short-sighted person tries to distinguish a distant object; and the upper orbicular muscles are at the same time slightly contracted. The wrinkling of the lower eyelids under these circumstances has been observed with some savages, as by Mr. Dyson Lacy with the Australians of Queensland, and several times by Mr. Geach with the Malays of the interior of Malacca. What the meaning or cause of this action may be, cannot at present be explained; but here we have another instance of movement round the eyes in relation to the state of the mind.

The vacant expression of the eyes is very peculiar, and at once shows when a man is completely lost in thought. Professor Donders has, with his usual kindness, investigated this subject for me. He has observed others in this condition, and has been himself observed by Professor Engelmann. The eyes are not then fixed on any object, and therefore not, as I had imagined, on some distant object. The lines of vision of the two eyes even often become slightly divergent; the divergence, if the head be held vertically, with the plane of vision horizontal, amounting to an angle of 2'0 as a maximum. This was ascertained by observing the crossed double image of a distant object.

Charles Darwin

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