If you were writing that the four friends in "Dr. Heidegger's Experiment" did not become young again, you could use the passage from page 50: "...the Water of Youth possessed merely a virtue more transient than that of wine." This passage supports the idea that the rejuvenating effects of the water were short-lived and temporary.
1. The passage mentions that the Water of Youth's virtue was more fleeting than that of wine, implying that its effects did not last long.
2. This indicates that the transformation of the four friends into youth was not permanent and that they did not stay young.
3. By referencing this passage, you can strengthen your thesis that the rejuvenation experienced by the characters was not a lasting change but rather a transient one.