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		Results At 5 days of development, the forelimbs and hindlimbs of the donor embryo appear as elongated protrusions from the embryo body (fig. 4). Staining with Alcian green allows visualization of cartilage formation up to this stage in development. The 5-day old and 7-day old embryos exhibited faint cartilage at the location of the future forelimb and hindlimbs (fig. 5a-b). Figure 4. 5-day old donor embryo before graft excision. Figure 5a. 5-day old embryo stained with Alcian green for cartilage development. Figure 5b. 7-day old embryo stained with Alcian green for cartilage development. Figure 6. Hindlimb graft derived from 7-day old donor embryo incubated on chorioallantoic membrane for 7 days. Figure 7a. Control forelimb of 12-day old embryo. Note the upper part of the limb is missing. Figure 7b. Control hindlimb of 12-day old embryo. Figure 7c. Control forelimb of 14-day old embryo. Figure 7d. Control hindlimb of 14-day old embryo. Of the 12 grafts attempted from 5-day old donor embryos in one experiment, none were successful. Of the 3 grafts derived from the 7-day old donor embryos, one was successful. Many of the embryos died from infection during the 7-day incubation period, as evidenced by the yellow-green appearance and odor of the egg contents. Of the embryos that survived, the grafts were difficult or impossible to locate, possibly because the grafts were concealed by membrane or lost in the liquid environment below the membrane. The only successful graft was a hindlimb derived from a 7-day old embryo. After the 7-day incubation period on the chorioallantoic membrane, the graft showed considerable cartilage development (compare fig. 5b, 6). However, only the most distal structures developed, compaared with the intact 7-day control embryos incubated for 7 days (fig. 7d). Though no grafts derived from 5-day old embryos or forelimbs from 7-day old embryos were successful, it is worthwhile to compare limb development in the controls that were prepared. After 7 days of incubation, the embryos were 12 and 14 days old, respectively. There is extensive cartilage and bone formation in both groups. Distinct joints can be discerned, as well as clearly distinguished digits in the forelimbs and hindlimbs (fig. 7a-d).