INHIBITION OF THE DEVELOPMENT OF THE BURSA OF FABRICIUS IN THE EMBRYOS OF THE COMMON FOWL BY 19-NORTESTOSTERONE1

0.63 mg. of 19-nortestosterone in 0.1 ml. of corn oil, when injected into the fertilized eggs of the white leghorn hybrid strain of chickens, “Wisco-white,” on the 5th day of incubation, completely inhibits the development of the bursa of Fabricius in both sexes. In the normal chick the bursal primordium appears as a proliferated epithelial mass dorso-caudal to the embryonal cloaca on the 5th day of incubation. By 168 hours of incubation it forms a tubular structure; its terminal end enlarges into a bursal vesicle on the 10th day and becomes lymphoidal by the 15th day. The bursa is fully formed and lymphoidal in 17- day old chick embryos. In 19-nortestosterone-treated embryos the bursal primordium becomes highly vacuolated. Later it remains as a convoluted, short duct without forming the bursal vesicle. Thus the hatched chicks arc bursaless. The secondary effects of this hormone on the rectal complex are the stunted growth of the ventral anal lip, increase of musculature in the dorsal lip and an attenuated proctodial canal with very few anal mucoid glands.