Fig. 4. Results at E4 of experiment B1 (see Fig. 1D1 and Fig. 3A-D). (A) Lateral view of a host chick embryo 2 days after the operation. The position of the graft is apparent from a notch at the cervical level. (B-E) Consecutive cross sections at the level of the graft, hybridized with Shh (B), Pax3 (D) or BMP4 (E) probes or treated with the QCPN antibody for detection of quail cells (C). In C, the neural tube (NT) and dorsal root ganglia (DRG) are indicated. Ao, aorta.