INTRODUCTION
This work was originally undertaken in order to discover possible physical and chemical changes occurring in blood serum during those disturbances of water balance which result in the appearance or disappearance of edema. During the course of these studies, 172 sets of determinations have been made, and this paper presents the data from twenty-eight observations on eighteen normal subjects. The pathologic material will be discussed later. As we have failed to demonstrate any consistent changes accompanying such disturbances of water balance, this publication must be, in the main, a statistical report. We have been unable to find in the literature any previous studies of a similar nature that would demand a detailed discussion here. They are, in general, considerably less complete than this work or they present definite errors in method. The older work is well summarized in H. D. Hamburger's "Osmotischer Druck und Ionenlehre." Certain physical properties of