As is well known, the lymphatics will absorb particulate substances, and also materials insoluble in water, whereas the blood capillaries are principally concerned with the absorption of materials soluble in water. This knowledge has resulted in much interesting experimental work bearing on the subcutaneous injections of certain insoluble materials which were found to have been taken up by the lymph vessels and carried to the lymph nodes. Many investigators have reported certain experimental results obtained by injecting insoluble substances, such as carbon and carmine, into the subcutaneous tissues of the legs of animals. They have been able to prove, by recovering them in the lymph nodes, that the lymphatic system absorbed these substances. While such results are interesting and important, we are unable to find experimental use of the roentgen ray in the living animal to visualize foreign opaque particles in lymph nodes. The collection of iodized poppy-seed oil in