"In walking the streets, how many persons of one's acquaintance are every minute presented to the mind, as their pictures are painted on the retina; yet if we be alone, having our thoughts strongly turned upon a particular subject, or else be deeply engaged in conversation with a friend, we are often not conscious of the presence of these people when before our eyes, nor remember their having been so, when they have left us."
An Essay on the Vital and Other Involuntary Motions of Animals
3 entries in ESTC (1751, 1763, 1768).<br>
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Robert Whytt, <u>An Essay on the Vital and Other Involuntary Motions of Animals</u> (Edinburgh: Printed by Hamilton, Balfour, and Neill, 1751). &lt;<a href="http://books.google.com/books?id=eCz7KJ_6XYIC">Link to Google Books</a>&gt;