Cyto- and myeloarchitectonics as well as acetylcholinesterase activity of the nucleus limitans thalami--an important part of the nociceptive system--were studied in insectivora (Sorex araneus, Erinaceus europaeus, Talpa europaeus), rat, rabbit, cat, monkey and man. Our results suggest that nucleus limitans is phylogenetically a rather new structure. In insectivora and in the rat we could not fi...