The Expression of the Emotions in Man and Animals public by arguing that humans had "animal traits", and instead charmed them by telling stories of "human traits in animals", thus avoiding too much explicit talk of natural selection at work. Darwin preferred to leave the evolutionary implications hanging. Korn points out that the book has never been out of print since 1872, calling into question Ekman's talk of "Darwin's lost masterpiece". The "Editor's notes" at the "Mead Project source page" on the book comment that Darwin concluded work on the book with a sense of relief. The proofs, tackled by his daughter Henrietta ("Ettie") and son Leo, required a
Darwin from Descent of Man to Emotions our work; and of these you rank as the first." With "the little strength left in me" he reopened his enquiries into earthworms, requesting information from correspondents. The 6th edition of "Origin of Species" was published by Murray on 19 February 1872 at a price kept down to 7s. 6d. by using minute print, and sales increased from 60 to 250 a month. Through the spring Darwin pressed on with "The Expression of the Emotions in Man and Animals", pointing to shared evolution in contrast to Charles Bell's "Anatomy and Physiology of Expression" which claimed divinely created muscles to express