Histological Observations on the Epiphysis Cerebri and on the Chorioid Plexus of the Third Ventricle of the Dog

The epiphysis cerebri has long been a subject of considerable interest and until only very recent time has its histological components been elucidated in several species. The physiological role of the epiphysis in the body has not yet been worked out. From time to time the histological as well as the physiological conceptions regarding this organ have changed. Galena (8) first regarded this organ as a gland. Later Descartes (6) regarded the epiphysis as the seat of the soul. These suggestions have been followed by others which consider the epiphysis as an organ with a purely mechanical role concerned with the circulation of the cerebrospinal fluid and as a rudimentary, degenerated, or atrophying organ without function. The histological interpretation of the epiphysis of several species of animals has passed through rather diverse stages. Until recently, data in regard to the fundamental constitution of its parenchyma in the human, monkey, cow, sheep, rat, and rabbit were not precise. It is the purpose of this manuscript to present the authors\u27 histological interpretation of the components of the epiphysis cerebri and of the chorioid plexus of the third ventricle of the dog. The literature pertaining to the histological components of these structures is very meager. It would seem logical that before the physiological role of these structures in the body can be thoroughly established it would first be necessary to elucidate the histological picture