Slide showing three diagrams showing 'the cellular structure of the testis' of a rat. Slide shows three diagrams showing 'the cellular structure of the testis' of a rat. The diagrams are labelled 'A', 'B' and 'C'. In diagram 'C', the nucleus is labelled also. Title below image reads: 'Fig 9 - the cellular structure of the testis. (A) Low-power microscopic view of the testis of a rat. (B) Diagrammatic view of part of the wall of a single tubule. (C) Stages in formation of a sperm from a single cell (spermatocyte) of the tubule.' Late 19th to early 20th century