[Enclosure]

Copy of a Letter from James Leask Sinclair to Sir Henry Holland   London 1869.

“Sometime in 1844, my attention was drawn to the subject of Psychology, by the study, or rather the perusal, of a little book of Forbes Winslow’s that I picked up in an Edinburgh Library.⁶

This thin volume was a great treat to me at the time, as it related chiefly to nervous disorders, and some passages in it on Dreams made a very serious impression on me.

Afterwards I read something on the same subject in Brougham’s “Introductory Discourse to Paley’s Natural Theology,”⁷ and this I made the basis of my own researches on the subject. From 1850 to 1862, I had leisure for such investigations, and I now beg to send you a brief summary of the results.—

Taking the impressions made upon the sense of sight during a day, I endeavoured to ascertain whether their reproduction in Dreams followed one or more laws, and I found, that, excluding such dreams as might be considered to arise from the state of the secretions, or from a temporary derangement of the digestive powers, they could be reduced to two, which I named “Lex Fortuitæ Impressionis”, or The Law of Oblique Impression (in Dreams), and “Lex Intensæ Impressionis”, or The Law of Intense Impression (in Dreams): in plain language, “The Law of Casual Impression,” and “The Law of Strong Impression.” In the former, the Impression enters, as it were, obliquely, or, at an angle; it is entirely unexpected, you were not seeking for it, and yet it is as liable to be reproduced as those deeper impressions which Shakespeare has so admirably depicted in his Romeo and Juliet

In 1860, & 1861, I studied the subject of Mesmerism, and arrived at another law, which I termed “Lex Habitus”, or Law of Habit. This Law is merely “That, in abnormal states of the body, the impressions made upon it, are in exact accordance with its habits in the normal state”. For instance, in the Mesmeric coma, a man speaks when his eyes are touched, not because the organ of language has been stirred, but because, from his earliest years, whenever his eyes were covered by a companion coming behind him, his first impulse has been invariably to speak. When touched on the side of the head, he may assume an offensive or defensive attitude, not because the organ of combativeness has been awakened, but because, from his earliest youth, he has been accustomed to be cuffed on the side of the head. When touched on the top of the head, again, he may appear to be elevated, not because the organ of self-esteem has been excited, but because he has been accustomed to be patted on the head in his youthful years, and the erect posture of the body that is necessary to sustain the head when touched in this way, is the ordinary attitude of people in whom sanity predominates.—”