Answer:
From the description of his study, I can conclude that Dr. Heidegger is a physician who is into sorcery and the use of magic.
Explanation:
From the short description of his study, we discover that the doctor uses a magic book which no one even knows the title. Anyone who uses magical book is not far from being a sorcerer.
We were also told that the spirits of his patients were kept within a verge. Even though it is said that it is fabled, but I believe there is truth in that. In the story, we are also told that he gave his four friends enchanted water to drink in order to restore them back to their youthful age. These point out that the doctor uses magic.
The short story, "Dr. Heidegger's Experiment" was written by Nathaniel Hawthorne, an American author.
