Figure 1.

The three-tissue layers of the chick mature CAM are indicated in the schematic representation in (a) and clearly recognizable at day 16 of incubation, after Toluidine blue staining (b): the chorionic epithelium (ce) adheres to the shell membrane (sm); the intermediate mesodermal layer (ml) contains blood vessels; the allantoic epithelium (ae) lines the allantoic cavity (ac). (a) Modified from Gabrielli et al. [30]. (b) Original magnification: 40x; scale bar: 8 μm; M. G. Gabrielli, unpublished.