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 Expression of the Emotions in Man and Animals with livestock breeders and pigeon fanciers; on observations on his infant son William Erasmus Darwin ("A Biographical Sketch of an Infant" - published as a paper in the philosophical journal "Mind"), on his family's dogs and cats, and on the orangutans at London Zoo; on simple psychology experiments with members of his family concerning the recognition of emotional expression; on the neurological insights of Duchenne de Boulogne, a physician at the Salpêtrière asylum in Paris; on hundreds of photographs of actors, babies and children; and on descriptions of psychiatric patients in the West Riding Pauper Lunatic Asylum at Wakefield in