In the study of the cytology of human and animal cancer the work of Hansemann is the first to receive the attention of the cytologist. The older cytological studies on various normal and pathological tissues of Virchow (1851), Eberth (1876), Arnold (1879), Martin (1881), Cornil (1886), Klebs (1889), Schottländer (1888) and others have been reviewed so often that no further mention need be made here.