Slide showing two microscopic diagrams of 'Pregnantriol' and 'Squalene'. Slide shows two microscopic diagrams labelled 'Pregnantriol' and 'Squalene'. Number 'XVIII' appears in the top left corner. Title below images reads 'Fig. 93 (continued). D. Pregnantriol. E. Squalene.' The letters 'h.n.t' appear above both diagrams. The letters 'i.n.t.' appear under lower part of each diagram. Late 19th - early 20th century