As a means of differentiating nephropathies, cardiopathies, arteriosclerosis and essential hypertension, Butterfield, Erdwurm and Braddock1 have employed certain physical methods of examining the blood serum, and they claim that each of these conditions is accompanied by characteristic changes that are of diagnostic value. During the two years which have elapsed since the publication of their paper, however, this method of examination has received little attention from clinical laboratories and workers. In order to secure data on the value of the method, we have applied it to a large number of serums, and the results of the investigation are incorporated in the present communication.
The following determinations were made: Refractive index, freezing point, specific gravity, total solids, inorganic salts (ash).
Method of Obtaining Serum.
—Blood was drawn between 10 and 12 a. m., the patient having had nothing but a hospital breakfast. It was allowed to clot. Serum was drawn off