In White Raiment by William le Queux

Twenty or thirty minutes elapsed before I regained my power of speech. The drugs administered by Hoefer fortunately had the effect desired. His sleepy eyes beamed through his great spectacles as he watched with satisfaction the stimulating consequence of the injection. He dissolved in water a tiny red tabloid, which he took from a small glass tube in a case he carried, and ordered me to drink it. This I did, finding it exceedingly bitter, and wondering what it was.

I asked no questions, however. He was a man who had made many extraordinary discoveries, all of which he had kept a secret. In the medical profession he was acknowledged to be one of the greatest living toxicologists, and his opinions were often sought by the various medical centres. Indeed, as every medical man knows, the name of Hoefer is synonymous with all that is occult in the science of toxicology, and the antidotes he has given to the world, from time to time, are as curious as they are drastic in effect.