This is a vintage anatomical diagram depicting a cross-section of a fetal rat's semicircular canal. The diagram is labeled with letters to identify different structures. The main structure is a roughly semi-circular shape, labeled 'A', with a central area 'B'. Within 'B', there's a dense arrangement of small, cell-like structures, resembling hair cells, with their bases connected to the tissue and their tops extending towards the center. These cells are arranged in a radial pattern. Around the outer edge of the semicircular shape, there's a curved structure labeled 'C', and along the top, there's another curved structure labeled 'D'. The diagram also includes smaller labels 'a' and 'b' pointing to specific areas within the structure. The entire diagram is drawn in a detailed, illustrative style, typical of anatomical drawings from the early 20th century. The text below the diagram reads: 'Coupe transversale de la crête auditive d'un canal semi-circulaire de fœtus de rat.' which translates to 'Cross section of the auditory crest of a semicircular canal of a rat fetus.'