Joseph Engel (1816-1899) was a Viennese anatomist and pathologist trained under the mentorship of Carl von Rokitansky (1804-1878), the man who laid the foundations of gross anatomical pathology. In 1839, Engel completed his first scientific project: the dissertation entitled "Über den Hirnanhang und den Trichter" (About the pituitary gland and the infundibulum). This work analyzed the pathological and clinical characteristics of the pituitary and infundibulum tumor specimens collected at the Vienna Pathologic-Anatomical Museum. This little-known work represents one of the earliest attempts to determine the function of the pituitary gland-infundibulum complex. Among the 12 pituitary/infundibulum tumors examined in Engel's dissertation, one of the cases (no. 10) was instrumental for the definition of hypophyseal duct tumors, or craniopharyngiomas (CPs). This huge cyst, approximately the size of a goose egg (6 × 6 × 4.5 cm), was found in 1828 during the autopsy of a 33-year-old patient who suffered from severe headache, blindness, apathy, and finally somnolence. The cyst had replaced the hypophysis and extended upwards into the hypothalamic region and downwards into the sphenoid sinus, its inferior pole protruding through the soft palate. In 1904, the Viennese pathologist Jakob Erdheim (1874-1937) re-examined this lesion and conclusively categorized it as a hypophyseal duct tumor after a detailed histological study. The original tumor specimen corresponding to this CP case is still preserved at the Narrenturm, the circular building within the old Allgemeines Krankenhaus (Vienna General Hospital) that today holds the pathological collections of Vienna's Federal Pathologic-Anatomical Museum. To the best of our knowledge, this tumor is very probably the oldest preserved whole CP specimen in the world. This paper presents a comprehensive review of Engel's dissertation, the pioneering pathological work on pituitary and infundibulum tumors which laid the groundwork for the proper clinical, topographic, and pathological categorization of craniopharyngiomas.