The endocrine factors concerned in the control of the ovarian cycle

EXPERIMENTAL studies upon the relation of the pituitary gland to the ovarian cycle in mammals involve three principal difficulties:(i) that of removing the pituitary itself without injury to the animal;(ii) the practical impossibility of removing the anterior lobe without removing or damaging the posterior lobe;(iii) the necessity of killing the' test animal, in most cases, to confirm whether injected extracts or transplants have produced ovulation or other changes in the ovaries.None of these objections arises, however, in the case of certain amphibia.In a recent series of papers by Hogben [1930], Hogben, Charles and Slome [1931] and Zwarenstein and Shapiro [1933] reporting work carried out on the African Clawed Toad (Xenopu8s laevis) it has been shown:(i) that ovarian atrophy follows removal of the anterior lobe alone; (ii) that injection of acid extracts prepared by the method elsewhere described by the writer [Bellerby, 1929] will induce the extrusion of eggs during the period of the year when the anirmal does not breed either in its natural