Figure 3. Immunostaining images for PCNA (A-H) and fMHC (I-L) in the anterior (A,E,I), middle (B,F,J), and posterior (C,D,G,H,K,L) regions of E15 (A-D) and E17 (E-L) tongues. Chronological changes in the PCNA-labeling index in mouse tongues between E11 and birth (M). D, H, and L are higher-magnification images of the regions indicated by the rectangles in C, G, and K, respectively.