The Homosexual Matrix the most novel account of the way in which behavioral expression communicates internal states since Charles Darwin's "The Expression of the Emotions in Man and Animals" (1872), but considered his most original contribution to be his explanation of how erotic feeling depends on "resistance", which might consist of any of several impediments to easy access to sexual satisfaction. Begelman called Tripp a skillful writer who was learned on the subject of homosexuality, but whose objectivity was nevertheless open to question. Karlen wrote that Tripp made numerous unjustified claims, such as that homosexual men tend to have a larger than average
The Variation of Animals and Plants under Domestication grown too long, & I think I shall publish separately a very small volume, 'an essay on the origin of mankind'". This "essay" would become two books: "The Descent of Man, and Selection in Relation to Sex" (1871) and "The Expression of Emotions in Man and Animals" (1872). The book had been advertised as early as 1865 with the unwieldy title "Domesticated Animals and Cultivated Plants, or the Principles of Variation, Inheritance, Reversion, Crossing, Interbreeding, and Selection under Domestication" but Darwin agreed to the shorter "The Variation of Animals and Plants Under Domestication" suggested by the compositors. By May he