The cellular picture in the anterior pituitary of normal fowls from embryo to old age

The need for a complete history of the cellular changes and activities within the anterior pituitary of the normal (nonexperimental) fowl from the embryo to old age is evident. The facts, if correctly described and interpreted, should aid in the solution of the complexity of problems which seem to be bound up in one way or another with the pituitary. The history which I shall give is based upon my own studies, in part published, but observations of other authors will be included. Correlations will be made with Breneman’s studies on pituitary and gonad weights and pituitary assays but otherwise a discussion of the literature will be reserved until sufficient data arc at hand to make discussions more profitable. Over a period of years a total of more than 1500 pituitaries from control and experimental birds has been studied. Large numbers are necessary to fill in the required stages and also because of variations in cell growth and activities which may occur a t any stage due to both internal and external factors. Pituitaries were collected a t 5-day intervals beginning with the first day after hatching and extending to the 125th day. From 125 days to old age the intervals were irregular. The White Ilegliorn fowl has been used in nearly all cases and unless otherwise stated descriptions apply to that variety. In describing cellular changes pituitaries have been selected which seem from all points of view to exhibit optimum conditions. There is an element of