THE DEVELOPMENT OF THE HYPOTHALAMO-NEUROHYPOPHYSIAL SECRETORY SYSTEM IN THE CHICK EMBRYO

Abstract

Brains of chick embryos in daily stages of incubation from 48 hours through 20 days were serially sectioned and stained with Gomori''s chrom-hematoxylin-phloxine to show neurosecretory substance. Adjacent sections were stained with periodic acid-Schiff, a silver nerve fiber stain and a tri-chrome stain. Representative chicks were fixed with Bouin''s solution, formol-saline, and formol-saline-sublimate. Bouin''s solution was the best fixative for the Gomori stain. Neurosecretory substance appeared in the neurones of the supraoptic region as early as 97 hours incubation and was present in the axones by 5 days incubation. The substance was found in the infundibulum by the 6th day, and it increased in concentration in the infundibulum throughout embryonic life. Material staining with PAS coincided in time and location with the appearance of neurosecretory substance. This may indicate that the neurosecretory substance has a polysaccharide component. The infundibular ependyma formed a cytoplasmic material staining with Gomori''s chrom-hematoxylin-phloxine early in development and then excreted droplets of this material into the ventricular cavity from the 14th through the 17th day of incubation. The significance of this phenomenon is unknown. Argentophilia is relatively slight in the embryonic chick hypothalamo-hypophysial tract as compared with certain other fiber tracts of the brain.