Arachnoidea and subarachnoid spaces of the vault of the skull in man.

This field is meagerly represented in the literature. The aim of this paper is to check in man the descriptions which for the most part were made in animals. Specimens were taken during the course of neurosurgical operations. Arachnoidea of the vault of the skull is situated beneath the subdural neurothelium previously described in man by the same authors. Its cells have epithelial features. Its extracellular spaces are more or less dilated and contain connective tissue fibers. Subarachnoid spaces appear as dilated perivascular spaces. Under the conditions in which human specimens were obtained, we cannot determine whether the cellular coverings of the deep surface of the arachnoidea are continuous. The adventitiae of the subarachnoid vessels contain an apparently continuous cellular sheath, which does not usually occur in other vessels. Arachnoid trabeculae are of uncommon occurrence. Their connective tissue fibers are isolated from the surrounding cerebrospinal fluid by an apparently continuous cellular covering.