STUDIES OF THE EMBRYONIC CIRCULATORY SYSTEM

Abstract

Using the yolk-sac blood vessels of the living 4-day chick embryo, it was found that the caliber of these is not detectably influenced by acid (p H 5.0) or alkali (pH 9.0). The vessels are, however, specifically reactive to CO2. The response is a constriction. The bearings of these findings on current theories and the developmental physiology of the chick are discussed.