Final answer:
The question seems to refer to a literary work, but the provided excerpts do not contain information about a character named Demetrius taking Marcellus to recover mentally; more context is needed to provide an accurate response.
Step-by-step explanation:
The student's question appears to refer to a specific narrative context, but without a clear reference to a particular work of literature, it's challenging to provide an accurate response. The provided excerpts mention several characters and scenarios from different texts, yet none include a character named Demetrius who takes Marcellus to recover mentally.
However, the name Demetrius is often associated with the play A Midsummer Night's Dream by William Shakespeare, where there is also a character named Demetrius. Still, without more context, any attempts to answer the question would be speculative at best. To give a well-informed and accurate answer, more details about the text or story in question would be necessary.