Results

Of the initial thirty-six 1-day old eggs opened, sixteen chicken embryos were successfully transferred to culture dishes in preparation for surgery. The rate of successful transfer was therefore 44.4%. After staging, four of the embryos were found to be at stage eight, four were slightly younger than stage eight, three were at stage six, two were at stage seven, two were at stage four, and one was slightly older than stage three. All embryos younger than stage eight were unsuitable for surgery. Because they had been transferred to a culture dish at such an early stage in development, the stage three and four embryos were unlikely to survive long enough for a heart to develop (Cebra-Thomas, personal communication).

Operations were performed on eleven chicken blastoderms when they were at or near stage eight of development. Two embryos were severed through their entire anterior portion, from the middle of the embryo through the entire forebrain. Seventeen hours after the first operation began, the control embryo was at stage 12 of development and had started to form a heart. Three embryos had reached stage 10, but the incision had begun to heal. These holes were surgically re-opened. One of these embryos was accidentally decapitated during the re-opening procedure and did not develop further. The embryos whose anterior half had been entirely bisected had not noticeably developed. One embryo at stage 13 had developed two distinct, beating hearts, while another of the same age was beginning to form two hearts. Of the remaining six chicken embryos, one failed to reach a heart-forming stage of development, and one incision healed before the heart developed. The three youngest embryos failed to develop normally. One had not progressed beyond the primitive streak, although the head had developed asymmetrically to the body. The second also had abnormal brain development.

By forty-four hours post operation, a third embryo had definitively formed two hearts (Figure 7). One embryo developed two hearts, which later fused at the ventricular end to form one abnormal heart whose two sides beat asynchronously (Figure 8). The hearts of all embryos in which cardia bifida was induced displayed asynchronous beating. Video footage of the three embryos with either two beating hearts or one abnormal heart was recorded. The vascular system was allowed to develop for ninety-six hours until circulation was visible (Figures 9 & 10). Observations were then stopped.

©Cebra-Thomas, 2000

Last Modified: May 2nd 2004

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