PHYSICAL PROPERTIES OF THE ALLANTOIC AND AMNIOTIC FLUIDS OF T H E CHICK II. HYDROGEN Iol~I CONCENTRATION BY PAUL ANDREW WALKER

The importance of the hydrogen ion concentration of the external medium of cells, tissues, and organisms has long been recognized. In the case of the developing chick, the external medium is represented by the amniotic fluid, and since the allantois soon surrounds the other components of the egg, its contained fluid must also be considered as a part of the embryo's external environment. This question of the hydrogen ion concentration of these extra-embryonic fluids has already received some attention, notably in the work of Aggazzotti (1913), Buytendijk and Woerdeman (1927), and Yamada (1933), but the results of these investigations do not agree, in part perhaps because the accuracy of the various techniques employed is open to question. Accordingly, it was considered desirable to reexamine this problem, using the glass electrode technique, which is admirably suited for use with small quantities of fluid. Haugaard (1934) further points out that the glass electrode can also be used in work with solutions containing carbon dioxide (as do both fluids under investigation) which can only be measured with the hydrogen electrode by the use of special devices.