Series of semi-thin sections were prepared of mature human placentas after immersion and perfusion fixation. Evidence was produced to the existence of syncytial bridges between neighbouring chorionic villi. Besides, syncytial knots and sprouts were present, as well as structures apparently similar to bridges which had resulted from peculiar cutting through a syncytial knot. The latter have been referred to as artefacts by other authors and are obtainable only under two conditions: 1. pre-existence of nuclear agglomeration at cutting level; 2. accidentally appropriate cutting. Such coincidence has been recordable from two thirds of all cases, but it is by no means responsible for all cases of bridge formation. Structures of that kind are never artefacts by any account of lexical meaning. The following criteria are suggested for differentiation between bridges, on the one hand, and structures resembling bridges due to tangential sections: 1. Number of nuclei relative to bridge surface; 2. Limitation of surface; 3. Appearance and arrangement of nuclei.