Percival Sylvester Bailey (May 9, 1892 – August 10, 1973) was an American neuropathologist, neurosurgeon and psychiatrist who was a native of rural southern Illinois.

He originally studied to became a teacher at Illinois Normal University, but transferred to the University of Chicago in 1912, where he became interested in neurology.

In 1918 he graduated from Northwestern University in Evanston, and in 1919 became an assistant to Harvey Williams Cushing at Peter Bent Brigham Hospital in Boston. In 1928 he became head of the neurosurgical department at the University of Chicago, and in 1939 was professor of neurology and neurological surgery at the University of Illinois. From 1951 he was director of the Illinois State Psychiatric Institute.

Percival Bailey is remembered for his collaborative work with Harvey Cushing, and his important work involving the classification of brain tumors, which prior to his research was in state of disarray and confusion. From 1922 to 1925, Bailey performed extensive pathological and histological studies of brain tumors, and based on cellular configuration, he created a classification system of thirteen categories. In 1927, he reduced the number of categories to ten.

In 1925, Bailey identified a mid-cerebellar glioma that is usually associated with childhood called a medulloblastoma, of which he published an important paper with Cushing titled Medulloblastoma Cerebelli. The two doctors are credited with coining the term “hemangioblastoma”.

With Paul Bucy (1904-1992), Bailey made investigations involving the structure of intracranial tumors and meningeal tumors. The two men were able to confirm that a specific type of tumor (now known as an oligodendroglioma) consisted of oligodendroglia. With Gerhardt von Bonin (1890-1979), Bailey authored two works, “The Neocortex of Macaca Mulatta” and “The Isocortex of Man”, which provided an accurate description concerning the cytoarchitecture of the cerebral cortex.

As a psychiatrist, Bailey was a vocal critic of Freudian psychology, which he considered speculative and unscientific. In 1965, he published a book about Freud titled “Sigmund The Unserene”.

§References[edit] Bucy, Paul C. “Percival Bailey 1892-1973”. Washington D.C.: National Academy of Sciences, 1989. Ferguson, Sherise and Maciej S. Lesniak. “Percival Bailey and the Classification of Brain Tumors”. Neurosurgical Focus. Vol. 18. No. 4. (April 2005).

Bailey of Cushing’s Clinic using the methods on the Spanish school of neurohistologists Cajal and del Rio-Hortega—has by means of their special staining reactions undertaken to arrange a classification oi gliomas. He has submitted a classification of gliomas comprising twenty types on the basis of their histogenesis.

In “Tumors of the Glioma Group by Bailey and Cashing” the authors present ll'lCll' classification and give their observations of the clinical course oi patients having these different cell types of tumors. As elsevrhere in the body the tumors which reproduce the more highly difierentiated cells grow ess actively and are relatively benign. Radical removal oi these is well repaid.

Three of the classified groups, viz., the oligodendrogliomas and the protoplasmic and fibrillary astrocytomas comprise about 40 per cent oi the gliomas. All oi these are relatively benign and thus warrant radical removal.

Predictions of certain types of glioma under some conditions may be made with some degree of accuracy. In our own experience the midline cerebellar tumors springing from the region of the roof of the fourth ventricle and occurring in children often gave vomiting as a first and only symptom over a considerable period of time, even many months, before other localiz' signs or gen- eral pressure signs appear; In theugasstfication of these authors these prove to be the medullo blas- tomas which, from a limited observation, seem to ¹⁾.

The textbook and atlas on stereotaxy, authored with Georg Schaltenbrand in 1959, remained a standard reference in stereotactic surgery until recent years.