The war was fought on other technological fronts, but after the ceasefire the quest for a more useable fatigue vaccine persisted in the dismantled and humbled Austro-Hungarian empire. Blood was still thought to be the key to curing fatigue and expanding the horizons of human usefulness, but the emphasis was now on the hormones that flooded it rather than the toxins that polluted it. It was Charles-Édouard Brown-Séquard, a professor of experimental medicine at the Collège de France and the grandfather of modern endocrinology, who brought the importance of these chemical cues in the blood stream to scientific attention. In 1889, aged seventy-two, he injected himself with the juice of pulped guinea pig and dog testicles, a hormonal fluid that he believed rejuvenated him. Though the concentrations of testosterone would have been too low to have any biological effect, Brown-Séquard claimed that he felt awash with new energy, that his brain functioned more quickly, that his endurance was enhanced, and his sexual potency revived. In a book he wrote about the experiment—Elixir of Life—he said he felt thirty years younger. He could work into the night, walk up the stairs without holding on to the banisters, and, he noted, his bowel movements improved.