The Living Cell in vitro as shown by Darkground Illumination and the changes induced in such Colls by fixing Reagents

Tissue growing upon a coverslip in vitro provides peculiarly favourable material for a microscopical investigation of the structure and behaviour of the living cell. Some of the changes which take place in the living cell during growth and division, as seen by direct illumination, have already been described by one of the writers (Strangeways, 1922). By employing dark-ground illumination, however, a much more intimate study of the cell growing in vitro can be made than is possible with the aid of the usual direct methed, and with this technique various internal structures appear as sharply defined, conspicuous objects which by the ordinary method are so indistinct as to be hardly visible. Dark-ground illumination, which has seldom been used for the examination of tissue cultures, has been employed by W. H. Lewis (1923), who records some interesting results obtained from a study of the living cell kept at room temperature. The present writers, by maintaining the cultures at body temperature throughout the period of examination, have been able to extend Lewis’s observations, and by the development of a special technique are also able to give some account of the changes wrought in the individual living cell by the application of some of the more common fixing reagents.