Western equine encephalomyelitis (WEE) virus is 40 to 55 m/z in diameter (1) and apparently contains nucleic acid of the ribose type (2, 3). Although electron microscopic examination of whole mounts of tissue cultures infected with a closely related agent (Eastern equine encephalomyelitis virus) has shown viral particles both within and on the surface of cells (4,5), no studies employing thin sections have been previously reported. The purpose of this communication is to illustrate and describe the manner in which WEE virus appears to differentiate within, and gain egress from, infected tissue culture cells as revealed in thin sections by the electron microscope. Similarities in development or release among WEE virus, influenza virus, herpes simplex virus, the virus associated with erythroblastosis of chickens, Rous sarcoma virus and a mouse mammary tumor agent will be discussed.
Stable human amnionic cells:A stable line of human anauionic epithelium was kindly supplied by Dr. Katherine Sprnnt. Replicate cultures were prepared in Leighton tubes without coverslip% using Eagle's basal medium with 10 per cent horse serum. The cultures were inocu-* These studies were aided