This non-fertile egg was observed using what is known as a candling procedure, whereupon, a very bright light is placed behind the egg, as was done throughout history by using a candle, hence the name. Today, employing more modern methods, a powerful lamp is placed against the broad end of the egg. In this way, the contents of the egg are revealed through the translucent shell. In unfertilized eggs, known as yolkers, the observer will see only a round yolk sac, and no developing embryo, or any blood vessels. Eggs known as quitters, are fertilized, but the embryo stops growing. In the case of quitters, one will note a thin blood ring encircling the yolk (PHIL 10148). Winners are eggs that are fertilized, and lead to the growth of a healthy embryo (PHIL 10149). In this case, one will observe blood vessels surrounding the yolk, and depending upon the length of gestation, one might see a dark shadow representing the developing embryonic eye.
<ul><li>Content Provider(s): CDC / Dr. Joseph McDade</li></ul>
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