Abstract
In previous experiments we found that, as a result of the daily injection of pituitary hebin in chicks over relatively short periods, testes and ovaries revealed considerable hypertrophy and as a result of this hypertrophy sexual ducts and head furnishings developed precociously. 1 However, in none of the treated female chicks, normal or ovariotomized, 2 did we observe a comparable response on the part of the rudimentary right gonad. In fact this organ revealed very little, if any, growth macroscopically even after relatively prolonged treatment, a rather significant fact in view of the pronounced response by the left ovary. We were, therefore, interested, among other things, in determining whether it was entirely nonresponsive to the gonad-stimulating principle of the hypophysis or whether it could be induced to respond significantly by treatment during the earlier embryonic period either before, or shortly after, morphological differentiation of gonads occurred.
Incubating eggs received single and repeated injections of pituitary hebin, the age of the egg at the time of injection determining whether the hormone was injected into the albumen or into the allantoic cavity. The volume of hormone injected varied from 0.05 to 0.3 cc. and the dosage from 5 to 30 rat units. Injections, which varied from one to 6 in number, were made at varying ages, daily or on alternate days, the earliest beginning at 48 hours and the majority terminating on the 9th day. In a few experiments injections were begun as late as the 12th and 14th day and terminated on the 16th day. Development was allowed to continue until the 18th day when surviving embryos were taken from the shell and examined, and material of interest was fixed for subsequent study.
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