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Avian Spare Yolk and Its Assimilation

1944; Oxford University Press; Volume: 61; Issue: 2 Linguagem: Inglês

10.2307/4079367

1938-4254

Alexis L. Romanoff,

Maritime Transport Emissions and Efficiency

IT is well known that at the time of hatching a bird still retains a portion of unassimilatcd yolk material.About two days before the embryo is ready to bc hatched, a rapid growth and unfolding of the tissues at the umbilicus cause that portion of the yolk which has as yet not bccn absorbed to bc enclosed within the abdominal cavity.After enclosure of the yolk, its utilization goes on as before until, under normal conditions, it has bccn entirely absorbed.Since the yolk sac is actually a divcrticulum of the small intestine, its material is absorbed directly from the sac into the blood stream.The spare yolk, in this manner, is able to supply the developing chick with a store of nutriment which enables it to survive for a limited period after hatching without an additional supply of food.The rate of assimilation of the spare yolk has bccn studied primarily in the chick (Virchow, 1891; Iljin, 1917; Schilling and Blccckcr, 1928; Parker, 1929; Jull and Heywang, 1930; Romanoff and Romanoff, 1933; Romanoff, 1943; and Fronda, Bancz, and Moncgas, 1937).Very little is known about the absorption of yolk in other species of birds as well as about changes in its chemical composition following hatching.For this reason the work was extended to include several species of birds and chemical changes in the yolk which, it was thought, might indicate preferential absorption of certain food material.