Final answer:
The detailed description of Dr. Heidegger's den with elements like cobwebs and antique dust is an example of a gothic setting. It uses imagery to create an eerie atmosphere while underscoring themes of decay and the passage of time.
Step-by-step explanation:
The description of Dr. Heidegger's den in paragraph 3 of "Dr. Heidegger's Experiment" vividly illustrates a gothic setting. The details presented, such as the room being dim, old-fashioned, festooned with cobwebs, and besprinkled with antique dust, are classic elements used to create an eerie atmosphere. These descriptors set a tone of decay and antiquity, which is typical for gothic literature. The description serves to immerse the reader in Dr. Heidegger's world and establish the themes of time, aging, and possibly the supernatural.
Moreover, the imagery employed by the author does not just define the physical characteristics of the space but also contributes to a larger thematic exploration of the narrative, which revolves around the consequence of interfering with natural processes, such as aging. The intricate descriptions also engage readers' senses, allowing them to visualize the scene while underlining the otherworldly and introspective nature of the doctor's character and his experiments.