IT IS a great privilege to report herewith a new method by which the liver and spleen are made roentgenologically visible following intravenous administration of a colloidal contrast medium. The results obtained in a series of cases in which this method was used will be described. The possibility of direct visualization of the liver shadow was suggested by the visualization of the gall bladder obtained by Einhorn (1), following administration of tetraiodophenolphthalein, and the use of tordiol later suggested for hepatosplenography by Oka (2) and Radt (3). This new colloidal contrast medium is not precipitated by the organic fluids and has been used for retrograde pyelography. After experiments on animals controlled by anatomic studies made by Dr. J. Rossier (4) in the Pathologic Institute of Prof. M. Askanazy, a clinically applicable method was developed which makes possible the roentgen visualization of the liver and spleen without risk to the patient. The author (5) has used this method on patients in Prof. M. Roch's University Clinic for Internal Medicine. Thorotrast is a 25 per cent thorium dioxide sol containing 22 per cent of metallic thorium. It has a bluish, milky, shimmering appearance in reflected light. In transmitted light it appears as a clear, brownish fluid. For intravenous use it is diluted at least ten times with 5 per cent glucose solution, sterilized by heating, and injected in increasing doses in the course of several days. To determine the patient's tolerance, an initial dose of not more than 0.1 gr. of thorotrast per kilogram of body weight is given. After that, each dose is increased from 0.1 to 0.05 gr. per kilogram of body weight until the desired dose is given, care being taken not to exceed the patient's tolerance. As a rule, a total of 0.8 gr. of thorotrast per kilogram of body weight is enough to produce an intense shadow on the roentgen film, the density of the liver being approximately equal to that of the vertebræ, and the density of the spleen to that of the ribs (Figs. 1 and 2). In the event that visualization of the margins of the liver and spleen is all that is desired, one-half to one-third of the dose is sufficient. Roentgen observation should be made 24 hours after the last injection, and a flat dorsoventral plate of the upper abdomen, taken with the patient in the supine position, is ordinarily sufficient. If the organs are abnormal in structure or position, special views are necessary, using a definite technic (6). The patient lies on the abdomen and the rays are directed dorsoventrally at an angle of from 20 to 30 degrees toward the patient's head, so that the liver is visualized in its greatest transverse and smallest vertical diameter. In the event that there is an appreciable variation from the normal position, the direction of the rays is correspondingly changed so as to be perpendicular to the plane of greatest diameter of the liver. The technic of Rieder and Groedel is applicable to the spleen.