Effect of Changes in Environment on Development of the Chick

Abstract

The work of Stockard in varying the normal environment of developing eggs with resulting malformations suggested carrying out similar experiments on a warm blooded animal, such as the chick. The eggs were placed in an incubator for 16 to 18 hours prior to operation. A piece of shell was removed, and in some instances 3 drops of 1/1000 solution of 95% alcohol were added to the side of the embryo, in others, 3 drops of normal saline (both at room and incubator temperatures), while a few eggs were carried along as controls. At various times, chiefly 48 and 72 hours later, the eggs were reopened and where embryos existed, they were fixed. Photographs were made and then the specimens were sectioned. The control eggs showed no abnormality. Of these 5 were completed for microscopic study; of them all fail to show a pituitary gland; 4 showed optic defects; 2 showed failure of closure of the head folds and in one no olfactory pits appeared. It made no apparent difference in the results whether the environment was changed with weak alcohol or normal saline solution. The treated embryos exhibited malformations of the nervous system. The abnormalities were chiefly (1) an absence of the pituitary gland, (2) in some an absence of an eye, (3) failure of the head folds to close, (4) in one, an absence of the olfactory pits.