Total Replacement of the Yolk of Chick Embryos

Isolation of the avian embryo from its normal food material is an essential step in a fundamental study of embryonic nutrition. With present methods, however, it has not been possible to grow embryos in culture for much longer than one day. In 1932 Waddington described methods of growing explanted embryos on serum clots. Several years later Spratt (1947, 1952) devised simplified media for embryos cultured on agar with which he studied various aspects of morphogenesis and carbohydrate needs of the young embryo. New (1955) has recently reported another technique for growing explanted embryos which allows development to proceed to about 60 hours, 40 hours of which are in vitro.