The Most Secret Quintessence of LifeLess than a century ago, physicians, scientists, and cultural commentators became fascinated by the endocrine glands and the effects of their secretions on our bodies and minds. Of all the characteristics supposed to be governed by them, the attributes of sex evoked the wildest interest. The gonads, it was revealed, secreted chemicals that not only influenced the biological expressions of sex, but seemed to generate the vitality and energy that made