Plate, corpus spongiosum urethrae, internal membrane of the urethra, and villi of the covering of the glans penis by Franz Bauer Plate XXI showing six figures. Three figures are of the corpus spongiosum urethrae, one is of the internal membrane of the urethra, and two show the villi of the covering of the glans penis. Subject: Anatomy Published in Philosophical Transactions as 'Observations on the human urethra, showing its internal structure, as it appeared in the microscope of F. Bauer, Esq'. Read 1 June 1820. [1820]