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The most serious point in the case is the disposition of the child." What on earth has that to do with it?" I ejaculated. My dear Watson, you as a medical man are continually gaining insight as to the tendencies of a child by the study of the parents. Don't you see that the converse is equally valid. I have frequently gained my first real insight into the character of parents by studying their children.

Arthur Conan Doyle (2012). “The Complete Sherlock Holmes: with an introduction from Robert Ryan”, p.844, Simon and Schuster
The most serious point in the case is the disposition of the child. What on earth has that to do with it? I ejaculated. My dear Watson, you as a medical man are continually gaining insight as to the tendencies of a