ENVIRONMENTAL MODIFICATION OF CERTAIN ENDOCRINE PHENOMENA¹

Study of the vaginal cycles of a group of $ rats after transection of the pituitary stalk has shown that unaltered, normal cycles are demonstrable in approximately half the animals. Pseudopregnancy, and short vaginal cornification after injs. of estrogens, were produced in these stalk cut rats. Approx. 1/5 of the operated animals displayed prolonged diestrous intervals. These prolonged cycles cannot be characterized as pseudopregnant cycles, however, since in this group the usual tests for luteal function were negative. Maintenance of $ rats in variously altered environments has shown that constant light causes constant follicular development without ovulation. Ovula-tion and pseudopregnancy were induced, however, by sterile mating. High external temperatures caused a depression of the thyroid cell height. Cold was followed by increased thyroid cell height and by enlarged adrenals. Simultaneous exposure to cold and light produced constant estrus, as well as adrenal and thyroid stimulation. All of these reactions, with the exception of the thyroid stimulation by cold, were produced in animals after pituitary stalk section. These results show that environmental stimuli may be transmitted to the ant. pituitary by routes other than the pituitary stalk. Furthermore they demonstrate that various endocrine components react in unitary fashions when the endocrine balance is altered.