The purpose of this article is to give the results of a comparative experimental study of the properties of the substances commonly used in pyelography, together with the clinical results obtained with sodium iodid. The use of this substance in roentgenography was first suggested by myself1 in 1918. A further study confirms certain observations and conclusions made at that time and also makes necessary certain modifications, which will be noted later.
In 1906, Voelcker and Lichtenberg2 reported the use of collargol in pyelography, and until recent years colloidal silver preparations have been used almost exclusively for this purpose. It was natural at first to consider colloidal solutions as exceptionally adapted for pyelography. For by such means, heavy elements which are relatively opaque to the roentgen ray could be introduced into the kidney pelvis in a comparatively innocuous state. An increasing experience, however, has shown that colloidal silver solutions