The Effect of the Thyroid on the Formation of the Hen’s Egg

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MANY environmental factors are known to influence the size of the hen’s egg, particularly nutrition (Parkhurst, 1933) and temperature (Bennion and Warren, 1933). Hays (1929) and others have also shown that weight of egg is inherited. Relatively little is known regarding the effect of specific substances on egg size. Riddle and Basset (1916) treated pigeons with alcohol and report that not only was the weight of the yolk in eggs laid during the period of treatment reduced, but the effect lasted for several months. No data were presented for untreated controls. Asmundson (1931) found that feeding hens dessicated thyroid caused them to lay smaller eggs, the effect on the yolk being most consistent. However, the effect in this case persisted for only about a week after thyroid feeding was discontinued and is probably not to be compared with the effect produced by substances such as alcohol. Since it appeared likely . . .