Pío del Río-Hortega
(Portillo, Valladolid, 1882 - Buenos Aires, 1945)

The prominent figure of Pío del Río-Hortega brings into question Ortega y Gaset's claim that Cajal was a unique, outstanding scientist who "arose by spontaneous generation.”  Cajal was, no doubt, the head of the Spanish Histological School, but Río-Hortega occupied, in all fairness, the second place.

He attended high school in Valladolid and obtained his medical degree at the University of Valladolid in1905. After a short experience as general physician in Portillo, he went to Madrid in 1909 for his Ph.D. His dissertation was entitled Causas y anatomía patológica de los tumores de encéfalo.  He worked briefly in Tello and Achúcarro’s labotaries, and then in Paris with Letulle and Prenant. He moved to the Institut für Infektionskrankheiten (Institute of Infectious Diseases) in Berlin, where he worked with Koch in bacteriology and experimental cancerology. The outbreak of World War I forced him to return to Spain via Holland. Both in France and Germany, Río-Hortega disseminated Achúcarro’s tannin and ammoniacal silver nitrate method. In his laboratory in Madrid, he developed his studies on cancer cells by applying Cajal’s techniques of gold - sublimate and urano- formol.

After a disappointing stay in England in 1915, Del Rio returned to Madrid, to the Laboratory of Histopathology of the Nervous System. When Achúcarro died, Del Río became head of the laboratory, but he did not get the post of assistant professor at the Faculty of Medicine, although he was appointed histopathologist at the Provincial Hospital of Madrid. In 1917, he discovered the method of silver carbonate and in 1919 one of the components of the nervous system, the third element: the microglia. A serious confrontation with Cajal and his colleagues forced Río-Hortega to move the Laboratory of Histopathology of the Nervous System to the Residencia de Estudiantes in late October 1920.

There he formed his disciples Vara López, Alberca, Salustio Alvarado, Isaac Costero, Llombart, and Ortiz Picón. In 1926, he became president of the Spanish Society of Natural History and published articles in its bulletin. After the discovery of silver carbonate method, Río announced the discovery of microglia and its mesodermal origin, unlike the ectodermal origin of neuroglia, at the First National Congress of Medicine (1919) and in four papers published in the Boletín de la Sociedad Española de Biología (1920). In 1928, he made a new discovery, the oligodendroglia that came also associated with a new and complex staining method: fixation with potassium dichromate and chloral hydrate followed by impregnation with silver nitrate, establishing their homology with Schwann cells. Its impact in scientific circles was extraordinary; Spatz successfully proposed that all elements of the microglia would be renamed "Hortega cells.” Internationally renowned scientists, such as Penfield came to the Residencia to "learn" from Río-Hortega. Also during this period, 1922-1928, Don Pío studied the histological constitution of the pineal gland, and he became reconciled with Cajal, who publicly acknowledged his accomplishments.

Between 1928 and 1936, Del Río worked on the Instituto Nacional del Cáncer and traveled all over the world. He was named director of the institute in 1932 and continued there the study, begun in his youth, of nervous system tumors, which culminated in a monograph on their microscopic anatomy (1933). At the outbreak of Civil War, Don Pío returned to Madrid and tried to save his research work at the Instituto del Cáncer that had been destroyed by bombs. By an order of the Republican government, he moved first to Valencia, then to Paris, and in 1937 to Oxford, where he created a laboratory almost identical to the one in the Residencia. The University of Oxford appointed him lecturer, made him honorary fellow of Trinity College, and granted him a doctor honoris causa.

In 1940, he arrived in Buenos Aires, where he established an important research center thanks to the contribution of the Institución Cultural Española, and founded the periodical Archivos de Histología Normal y Patológica. In 1943, he was awarded a doctor honoris causa, and was appointed Emeritus Professor at the University of La Plata. He died of cancer in June 1945. Del Río-Hortega was nominated twice for the Nobel Prize. The Consejo Superior de Investigaciones Científicas  (CSIC) published his memoirs entitled El maestro y yo (1986) in which he dealt with his discoveries and gave an account of his difficult relations with Cajal.