Histology of the ventral abdominal wall of E17.5 fetuses. All layers of the secondary wall were developed in WT (left panels) and KO (right panels). Magnification: 1.25× (A); 5× (B and C). u., umbilical. The content of the herniation was removed in this KO fetus; arrowheads indicate panniculus carnosus, which appeared discontinuous in KO and was further away from the midline compared with WT (arrows). 1, rectus abdominis; 2, transversus abdominis; 3, obliquus externus; 4, obliquus internus. Representative images of two Cald1^+/+, four Cald1^−/−, and two Cald1^+/− fetuses. Scale bars are incorporated in the figures.