Neurohumoral Control of the Pituitary in the Fowl

IN THE domestic fowl approximately 23 to 28 hours elapse between ovulation and the laying of the finished egg. During the intervening period the ovum acquires albumen in the magnum and shell membranes in the isthmal portion of the oviduct. This is accomplished in 4.5–5.0 hours and the remaining time is spent in the shell gland where the calcifierous shell is deposited. Warren-and Scott (1935) showed that ovulation does not usually occur while there is an egg in any portion of the oviduct. These facts and the finding that, in hens laying daily, ovulation takes place within 30–60 minutes after oviposition, led to the assumption that an intricate timing mechanism may be involved to synchronize reproductive events in chickens. An observation in this laboratory that injury to the oviduct led to a profound upset in the laying cycle of hens caused more intensive analysis of the relationship between events in the oviduct and the endocrine function of the pituitary.