Sex Energy: The Sexual Force in Man and Animals, Robert S. De Ropp, Delacorte Press, 1969, First Printing, Hardcover, 8.25×5.5×1″, 236pp. De Ropp was a noted biochemist, adventurer and involved in the work with Gurdjieff and Ouspensky.
https://gurdjieffclub.com/en/robert-s-de-ropp/

GOOD condition… No DJ, Black covers show wear at spine top and bottom, bookshop stamp and old price inside front cover, biding tight and square, pages clean and supple with a couple dog eared and occasional marginal notations in pencil or pen, and a few with pink underlining.

A complete book on sexuality in nature and in humans. Chapters include: Big Sex and Little Sex, Varieties of Sexual Union, Sex Energy Deified, Sex Energy Degraded, and Sex Energy in the Future.