Induced Ovipositions in Relation to Age of Oviducal Egg in the Domestic Hen

Summary Hens carrying oviducal eggs were injected with 0.30 unit of Pitressin at times equivalent to 1, 5, 9, 15, and 19 hours of time passed by the egz in the uterus. The percentages of birds laying prematurely were respectively 14, 32, 50, 51, and 56. Removal of the ruptured iollicle shortly aitcr reached its almost maximum size. The reovulation did not alter the response at the 19th hour in the uterus stage. The begining of the plateauof the response curve approximately coiilcided with the time at which theoviducal egg hecarne fully plumped, i.e. reached its almost maximum size. The response curve was interpreted as the expression of a change in the mechanical relationsbetween the uterus and the contained egg, rather than a change in intrinsic sensitivitydue to the action of the ruptured follicle.