Blood Cells in the Bone Marrow of the Chick Before and After Hatching

DURING the course of certain studies on the resistance of chicks to the pullorum disease (Roberts, Severens, and Card, 1939), data were collected on the blood cell activity in the bone marrow of chicks during the period of six days before hatching and seven days after hatching. The data presented here show the quantative changes in the blood cells of the bone marrow and circulation during this critical period in the development of the chick. METHODS Blood samples for cell counts of the circulating blood were drawn from the vitelline vein in the case of embryos and from the wing vein in case of hatched chicks. The chicks were killed with ether and both femurs and tibiae were dissected from the chicks and embryos. As soon as all adhering tissue had been removed from the bones, they were split in half along their longitudinal axis and immediately immersed in oxalated . . .