**Knowledge‑graph extraction from the PINAX metadata file**  

```cheimarros
# The PINAX record describes the aggregate Drexel collection
@file_pinax -> describes -> @drexel_historical_medical_collections:collection {
    title: "Drexel University Historical Medical Collections",
    creator: @drexel_university,
    institution: @drexel_university,
    created: "1849-1851",
    language: "en",
    subjects: [
        @medical_history,
        @nineteenth_century_medicine,
        @medical_education,
        @medical_theses,
        @historical_documents,
        @medical_instruments,
        @women_in_medicine,
        @homeopathic_medicine
    ],
    description: "A collection of historical medical materials from the 19th century, including theses, medical texts, and images from various collections held by Drexel University.",
    source: "PINAX",
    access_url: "PLACEHOLDER",
    rights: ""
}

# Explicit temporal scope for the aggregate collection
@drexel_historical_medical_collections -> time span -> {start: @date_1849, end: @date_1851}

# Geographic scope (already defined, reiterated for completeness)
@drexel_historical_medical_collections -> places -> [@pennsylvania, @new_jersey, @new_york, @england, @scotland, @united_states, @philadelphia]
```

---

### Synthesis across the Drexel sub‑collections  

```cheimarros
# 1. The aggregate collection unifies four distinct sub‑collections
@drexel_historical_medical_collections -> includes -> @ellis_collection_1851:concept
@drexel_historical_medical_collections -> includes -> @hunt_1851_collection:document
@drexel_historical_medical_collections -> includes -> @engle_thesis_collection:document
@drexel_historical_medical_collections -> includes -> @gardiner_thesis_collection:document

# 2. Temporal chain showing the rapid development of 19th‑century medical discourse
@engle_thesis_collection -> created on -> @date_1849_02_25
@gardiner_thesis_collection -> created on -> @date_1850
@hunt_1851_collection -> created on -> @date_1851
@ellis_collection_1851 -> created on -> @date_1851

# 3. Thematic recurrence of “women in medicine”
@women_in_medicine -> discussed in -> [@engle_thesis_collection, @hunt_1851_collection]

# 4. Centrality of medical education across three theses
@medical_education -> central to -> [@engle_thesis_collection, @hunt_1851_collection, @gardiner_thesis_collection]

# 5. Medical‑instrument focus linking Gardiner’s obstetrical‑forceps thesis to Ellis’s image set
@medical_instruments -> examined in -> @gardiner_thesis_collection
@medical_instruments -> illustrated in -> @ellis_collection_1851

# 6. Institutional context
@drexel_university:organization -> holds -> @drexel_historical_medical_collections
@drexel_university -> located in -> @philadelphia
```

**Resulting synthesis**

- The **aggregate entity** `@drexel_historical_medical_collections` (described by `@file_pinax`) binds four 19th‑century medical sub‑collections into a coherent whole.
- A **temporal chain** runs from the 1849 Engle thesis, through the 1850 Gardiner thesis, to the 1851 Hunt thesis and Ellis image set, illustrating the swift evolution of medical thought, education, and instrumentation within a three‑year span.
- **Thematic chains** reveal persistent emphasis on *women in medicine* and *medical education* across multiple collections, while *medical instruments* serve as a concrete link between textual analysis (Gardiner) and visual documentation (Ellis).
- The collection’s **geographic breadth** (Pennsylvania, New Jersey, New York, England, Scotland, United States) underscores the trans‑Atlantic character of 19th‑century medical discourse, all housed at **Drexel University** in Philadelphia.