The arachnoid or intermediate membrane consists essentially of an interlacement of flattened bundles of fine fibrous tissue interspersed with elastic fibers and platelike cells. In addition to the main sheath or the partition, both sides of which are covered with endothelium, numerous trabeculae extend across the subarachnoid space; in places they are so plentiful as to convert the cleft into a spongelike structure. Morphologically, these covering cells of the leptomeninges are low and flat with large, pale, oval nuclei. The chromatin net in the nucleus as a rule is indistinctly made out. With ordinary histologic stains the cell boundaries are not visible, but definite intercellular lines may be demonstrated by silver nitrate (Key and Retzius,1 and Essick2). Fatlike material in the arachnoid cells was described by Key and Retzius.
The purpose in this study was to determine the origin of the meningeal cellular elements, primarily the macrophages, in
STONE TT. LEPTOMENINGITISFORMATION OF MACROPHAGES FROM ARACHNOID CELLS. Arch NeurPsych. 1930;23(1):106-113. doi:10.1001/archneurpsyc.1930.02220070109005