A synthetic density gradient technique has been applied to the study of the PR8 and Lee strains of influenza virus in the angle centrifuge. The method counteracted convective disturbances and permitted about a fiftyfold improvement in clearing supernatant fluids of virus. Sedimenting boundaries of infective virus particles, hemagglutinin, and complement-fixing antigen were obtained in the angle...

Polysaccharides which cause inhibition of the multiplication of mumps virus in the allantoic sac may or may not cause inhibition of hemagglutination by the virus. Moreover, such substances may or may not prevent adsorption of the virus by erythrocytes. The available evidence indicates that polysaccharides active as inhibitors do not block adsorption of mumps virus by cells of the living allanto...

Rat embryos explanted with their membranes at head-fold stage (9 1/2 days gestation) formed an allantoic placenta which enlarged in culture and developed a foetal blood circulation. Embryos explanted at early somite stages (10 1/2 days) also formed a growing allantoic placenta but only after removal of most of the ectoplacental trophoblast. Assays of total protein in the embryo and placenta sug...

The chorio-allantoic membranes of White Leghorn chick embryos at 10 to 12 days after laying were fixed in Palade's buffered osmium tetroxide or in Luft's potassium permanganate. After fixation in these two ways the general appearance is similar, but there are differences in certain tissue elements. Cell membranes are well preserved after fixation in KMnO4. Certain lipid inclusions in the cytopl...

Distribution of water and of Na+ and Clions in blood and in allantoic, amniotic, and yolk sac fluids were observed during ontogeny of the chick embryo. A possible osmoregulatory role for pituitary hormones was inferred from differences in ionic concentrations and volumes of these compartments in partially decapitated (hypophysectomized) embryos and in intact and windowed-control embryos observe...

MANY of the unicellular organisms have a greater concentration of osmotically active material within their body fluids than there is in the medium surrounding them, and the higher animals have glands like the kidney and sweat glands which are able to elaborate fluids with much lower concentrations of sodium and chloride than the body-fluids from which they were derived. The concentrations of so...