Fetal azygos pericallosal artery.

An unpaired trunk forming part of the anterior cerebral arteries, the so-called azygos pericallosal artery, was found in a male fetus among a collection of 200 fetuses. The morphological characteristics of the trunk and the anterior cerebral arteries at the "preazygos" and the "postazygos" segments were examined using an operating microscope. The azygos pericallosal artery distributes into three postazygos segments of which only the median postazygos segment or median callosal artery had a bihemispheric distribution of its branches to the medial telencephalic surfaces.