A nontrivial aspect of early twentieth-century Western masculinity is the popular reception and educational relaying of early endocrine concepts of sexual development after 1889. "Internal secretion" relocated long-standing mono-causal attributions of sexual maturation and differentiation-the grand story of boy-to-man "development"-from "reabsorbed" semen to a conjectured "second" testicular secretion. US sex-hygienic works (1870s-1940s) readily reveal the long-term survival of the "old", semen-based, physiology of sex/gender as well as its behavioral-hygienic implications concerning "semen loss," a survival animated by various attempts at containing and interpreting transpiring scientific opinion. These discursive maneuvers provide a historical backdrop to present-day quasi-scientific valorizations of continence recirculated under the heading of "semen retention," valorizations posing important but unanswered questions concerning boyhood health-scientific literacy and what may be shifting, post-gonadal psychophysiologies of male identity.