Mongolism, like acromegaly, exophthalmic goiter, cretinism and many other diseases deeply affecting the personality of its victims, may be diagnosed clinically at a glance. This fact gave rise to its quick recognition throughout the world after the name was coined by Langdon-Down1 in 1866, and the literature became flooded with case reports and general articles on the subject. These, however, dealt with it largely from the clinical, statistical, sociologic and etiologic points of view.
The pathologic anatomy has received much less attention. This is especially true of the finer histology of the nervous system, and individual studies directed toward this point have usually been made on relatively few cases; moreover, the observations of various authors have often been contradictory.
The present report is based on a study of the brains from ten patients with mongolism found in the collection of the Staatskrankenanstalt-Friedrichsberg in Hamburg, and has been made possible