In the years 1952-1955 we had the opportunity to observe the development of an epidemic of fulminant infectious hepatitis in the city of Abancay, capital of the department of Apurimac (Peru), preferably in children, Aboriginal or not, the city and its environs. Anatomical material from some of these cases was sent to the Pathology Laboratory, Faculty of Medicine, the Professor, Dr. Peter Weiss, made the histological diagnosis of the disease. Shortly afterwards, and the good offices of Dr. Ramón Montenegro the Bureau of Lima, part of that material was sent to the Instituto Oswaldo Cruz, Rio de Janeiro, where the Head of Virus Section of Pathology, Dr . Madureira Pará, confirmed the diagnosis of infectious hepatitis.

The histological changes of the brain and of the other organs of the patient who was admited to the Psycopathic Hospital de la Magdalena del Mar, has been studied. The patient was admited to the hospital thirty years ago with the diagnosis of Demencia Precox. The discharge diagnosis was Maniac Psychosis. The examination showed lesions of Luetic endoarteritis of the small vessels of the cortex, an entity which was first studied in 1903 by Nissl and Alzheimer. It has been demostrated alterations in the vessels, meninqes, ganglion cells, and gliotic elements of the brain, and structural changes of the other organs. The predominant changes in the meninges are of a chronic and acute character. The former are old "alterations together with vascular sclerosis. The latter are peri-vascular infiltrations of phagocitic wandering cells in which it is frequent to find dense el elements of angular co...