[Histological research on rabies in the 19th century]

From 1872 to 1887, several works were published in which rabies were described as if they were only connected with blood-vessels and interstitial tissue, and so the disease was considered as a circulatory one, affecting the nervous system only secondarily. The histological study of the nervous system by Babès (1887), started off the second period of the microscopical study of rabies lesions. He directed his investigations towards the motor nuclei of the bulb, the medulla and the periventricular grey substance and individualized "rabic nodules', which presence, however, is not always noticeable. As contrasted with Babès, Van Gehuchten and Nelis (1900) demonstrated the occurrence of ganglionic lesions (peripheric, cerebrospinal and sympathic ganglia) which seemed constant and therefore having an incontestable diagnostic value. But it was only in 1903 when Negri discovered the corpuscules, bearing his name, in the cells of the Ammon's horn of rabic animals, that it was possible to establish an accurate cytological diagnosis of rabies. However, his interpretation (parasites belonging to the Protozoa) proved to be wrong.