Résumé
Two methyl methacrylate corrosion casts prepared from the intra-microvascular system of human brain-stem were used for the observation of morphological features of the system. Arterioles, venules and capillaries have their own morphological features respectively, so it is not difficult to distinguish one from others. Besides different forms of impressions formed by the endothelial cells nuclei on the surface of larger arterioles and venules, there are semicir cular impressions formed by the smooth muscle cells on the surface of larger venules and the majority of larger venules take a looplike shape on their way to pass forward. All these characteristics could be used to distinguish the larger venules. There are anastomoses between arterioles and between venules, with some A-V communicating branches between arterioles and venules.