Premature Expulsion of Eggs by Hens Following Injection of Whole Posterior Pituitary Preparations

Time of Oviposition as Affected by Neuromimetic Drugs

“…Even with large doses (50 mg.), which produced marked distress among birds, only 62% laid softshelled eggs. Somewhat similar variations in the premature response to posterior , pituitary preparations were found by Burrows and Byerly (1942) particularly with regard to route of injection and the position of the oviducal egg at the time of injection.…”

“…The data suggest that the musculature of the hen's uterus is innervated by both cholinergic and adrenergic fibers, both of which are apparently involved in maintaining the normal tone of the tract. Whether the autonomic system, histamine, or posterior pituitary substances (Burrows and Byerly, 1942) are involved in the regulation of normal oviposition remains undetermined. The ruptured follicle has been shown to influence normal oviposition (Rothchild and Fraps, 1944) but the mechanism of its action is unknown.…”

Photocontrol of Oviposition in Gallinaceous Birds *

“…Pituitrin (containing mainly oxytocin) injected intravenously in volumes to 0.2 ml. was effective in causing premature expulsion of hard-shelled eggs, according to Burrows and Byerly (1942). Oviposition occurred three to four minutes following injection.…”

Cholinesterase in the Diencephalon of the Hen in Relation to Egg Laying

“…Premature oviposition with a parasympathomimetic drug (Weiss and Sturkie, 1952) or the irritation of uterus by a loop of thread (Sykes, 1953), and delayed oviposition with sympathomimetic drugs (Weiss and Sturkie, 1952;Sykes, 1955) suggest the involvement of nervous factors in the regulation of oviposition in the hen, although it remains undetermined whether the nervous factors act on the uterus directly or through the release of posterior pituitary hormones which in turn cause oviposition (Burrows and Byerly, 1942;Burrows and Fraps, 1942). In the hen, as in mammals (Harris, 1955), the secretion of pituitary hormones is considered to be under the control of the central nervous system, diencephalon, through hypothalamo-pituitary pathways.…”