Nicolás Achúcarro (1880-1918), and the neuropathology laboratory he built in Washington
The Spanish neurohistologist who spent 1908 to 1910 at the Government Hospital for the Insane in Washington, organised one of the earliest laboratories for systematic neuropathology inside an American psychiatric institution, and went home to invent the tannin and ammoniacal silver method of 1911. He did not name microglia and did not define oligodendrocytes - his pupil Río-Hortega did both - and he was dead at thirty-seven.
Why this wins its question: English-language accounts of the discovery of microglia begin with Río-Hortega in 1919 and treat Achúcarro, if at all, as a name in the acknowledgements; accounts of Spanish science treat him as a lost genius. This object does neither. It puts on the record the two years he spent inside an American public asylum and what he built there, the 1911 method and exactly which cell types it could and could not separate, Cajal's own verdict that the staining was partial and inconsistent, the question of glial origin he could not answer, and the sentence in which his own advocates concede that the discoveries belong to his pupil - each bound to a peer-reviewed paper, with the advocacy of those papers declared rather than borrowed.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
Nicolás Achúcarro y Lund lived from 1880 to 1918 and trained across four countries before he was thirty - Madrid, Paris, Florence and Munich - and in Munich he worked under Emil Kraepelin and Alois Alzheimer, which gave him both a clinical psychiatry and an experimental neuropathology. In Paris he met Charcot's model of a neurological clinic in which observation at the bedside and anatomy under the microscope were the same enquiry.
Between 1908 and 1910 he worked at the Government Hospital for the Insane in Washington, D.C., the institution later known as St Elizabeths, on Alzheimer's recommendation. The source states that there he organised one of the earliest laboratories dedicated to systematic neuropathological investigation within an American psychiatric institution, and that he contributed to some of the earliest descriptions of Alzheimer-type pathology reported in the United States.
The claim of priority for those American cases is reported here at the strength its source gives it and no higher. Matute and Pacheco write of "some of the earliest descriptions", not the first, and they rest the point on a separate historical paper on the Spanish school and the first American cases of Alzheimer's disease rather than on the case records themselves. Nothing in this object rests on the hospital's own archive, which was not consulted.
He returned to Madrid in 1910 and in 1911 published the tannin and ammoniacal silver nitrate method, a refinement of the silver impregnations of Cajal's laboratory. Its effect was to make glial processes and reticular structures visible where cell shapes had previously been indistinct. In 1913 he joined Cajal's laboratory as director of its Laboratory of Neuropathology.
What the method showed was a population of cells nobody could classify. Working on rabbit brains infected with rabies or carrying inflammatory injury, Achúcarro described cells he called granuloadipose, concentrated around the lesions, and could separate phagocytic, granuloadipose and non-fibrous rod cells from stellate cells - in modern terms, microglia from astrocytes. He read their elongated rod shape as evidence of active movement among the degenerating neurons and proposed that their function was to phagocytose the damaged cells.
He also treated glial reaction as a disease process in its own right. In rabies, in paralytic dementia and in senile pathology he described morphological transformations of glial cells - amoeboid forms, rod-shaped cells, perivascular proliferations - without the immunological vocabulary that exists today; the second source used here states that he was the first to suggest that glial malfunction could itself generate disease without the neuron being damaged first.
His study of the cornu Ammonis and the fascia dentata was a glioarchitectonic analysis of the hippocampus - the distribution and vascular relations of glia across cortical subfields - at a time when cytoarchitectonics was standard and the glial equivalent was essentially unexplored.
The limits were real and are stated by the sources rather than inferred here. Cajal himself judged that Achúcarro's staining produced partial and inconsistent labelling. Achúcarro could not settle where the cells came from: he saw evidence for an ectodermal derivation and later suspected that circulating monocytes contributed to the brain population, and the techniques of his decade could not discriminate between the two.
The discoveries themselves are not his, and the source that argues hardest for him says so in its own words: he did not name microglia, he did not formally define oligodendrocytes, and those discoveries "are rightly attributed to his disciple Pío del Río-Hortega". Río-Hortega's silver carbonate method of 1916-1917 was a modification of Achúcarro's approach, and it was that method which resolved microglia from the cells he first called interfascicular and later oligodendrocytes. Wilder Penfield confirmed Río-Hortega's priority in 1924.
Achúcarro died in 1918 at the age of thirty-seven. The case his advocates make is architectural rather than proprietary - that without the technical and conceptual conditions he assembled, neither of Río-Hortega's discoveries would have been visible - and it is offered here as their assessment, not as an established fact, because both papers that make it are written to argue that the Spanish school is under-recognised.
That under-recognition has a documented cost attached to it that is not Achúcarro's alone. Charles Sherrington wrote in 1935 that it was no exaggeration to say that Cajal "with his pupils, especially Achúcarro, Hortega, and de Castro, opened a fresh era of knowledge"; the Spanish Civil War then dispersed the same school, Lafora and Río-Hortega and most of his direct disciples into exile, Villaverde assassinated in revolutionary Madrid, Tello and de Castro demoted for their liberal ideas and left to work under serious limitations, and the journal Archivos de Neurobiología closed by the authorities in power at the end of the war in 1939.