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A secondary demyelination process was brought about in the optic tract by unilateral enucleation of 10 adult rats which were sacrificed at 8, 15, 20, 30 and 45 days respectively, after the intervention. The Marchi reaction, which is identifiable by the presence of granular bodies, is positive at all stages, but tends to lessen towards the 45th day. The granular bodies are inside the disintegrating myelin sheath, and gradually fill the space made available by the degenerate axoplasm. The granular bodies are at first bulky and compact before breaking up and disappearing. The remains of the myelin sheath are then resorbed. Satellite cells occur from the 15th day onwards. The interest of the Marchi reaction for the tracing of nervous pathways is confirmed by these findings.

Two distinct categories of facts are deduced from a neuropathological study of the Ammon's horn, in particular the Sommer Sector, afflicted with alcoholic cirrhotic encephalopathy. In the pyramidal neurons of the CA1 layer, there are unquestionably paired filaments in a helical form, which correspond to the now classic "paired helical filaments". On the other hand, whereas the astrocyte population on the whole displays the characteristics of what can be called Alzheimer type II cells, a certain number of highly reactive areas persist, which can be detected by a GFAP-specific immunohistochemical method.

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