The AA. made a detailed histological analysis of the sympathetica tumors, by the study of six cases. These tumors are classificated as: sympathogoniomas, sympathoblastomas and sympathocitomas, accordingly to Pick and Bielschowsky. The last group has Rio Hortega's altered denomination. The AA. describe the most important facts of the clinical symptomatology, putting in evidence the fact that the two first groups of the classification are malignant tumors, and the last benign tumor. The sympathogoniomas have the clinical and anatomical appearance of sarcomas, with whom they only differ by subtile microscopical characteristics. The sympathoblastomas are of small dimension' and remain isolated; all the same they give big metastases at distance. Those of the adrenal glands form metastases following definite forms: Hutchinson type, principally in the skull, Pepper type, especially in the liver. The sympathocitomas reach big dimensions without producing symptoms, developing during years. The two first malignous tumors are more frequent in children and young people, the last one in middle aged people. After describing the classical facts, the AA. draw our attention on the following particularities: a) There exist many elongated schwanTilike cells besides the connective framework and the nervous elements. The silver impregnation showed, in the cytoplasm of those cells, similar fibrils to those described by Rio Hortega in the cells of the neurinomas. These cells are considered by the AA. as schwannlike cells. They explain their presence by the common derivation of the neural crest; b) The presence of other cells, whose precise nature could not be determinated, was also observed. Some had small and very dark nuclei and an abundant cytoplasm, others had clear nuclei of the neuroglical type, and very little cytoplasm. The AA. consider those cells as belonging to the neuroglia of the sympathetic ganglia (Rio Hortega's "espiro-citos"). c) A detailed study of the tumor's fibers was made. The existence of an abundant fibrilary framework with particular characteristics was observed besides the collagenous tissue of the capsule and some septa and the medullated and non medullated nervous fibers. The Van Gieson stains those fibrils in yellow and the Mallory in red. The Mallory shows a better collagenous reaction than the Van Gieson. The Hol-zer stains them in blue and the Perdrau in red. The Bielschowsky-Gros method reveals that they are a fibrilary differentiation of the schwannlike cells cytoplasm.
