A review of the literature is given, followed by a consideration of the available methods of demonstrating the lymphatic system in the area of the teeth and jaws.

A new method of demonstrating this system by the injection or application of lead acetate intra vitam, is described, and the technique is explained. The method can be employed to reveal macroscopic or microscopic lymph channels in any part of the body, and is especially of value where decalcification of the hard tissues has to be carried out in the preparation of the sections.

The various types of experiments which have been performed are described, and the macroscopic and microscopic results dealt with separately.

Among the macroscopic results, the lymphatic drainage of various parts the jaws is described, and the large amount of anastomosis and cross anastomosis between the vessels is shown. A comparison of the lymphatic system in this region in the guinea-pig, cat, dog, and monkey is given, and it is demonstrated that the guinea-pig and monkey possess submental and supraclavicular lymph nodes which assist in the drainage of this area in addition to the submaxillary and cervical groups of nodes possessed by the cat and the dog.

Among the microscopic results, the way in which the mass makes its way from the gingival tissues through the bone, and is found in the pulp, dentine, and cementum of the tooth, even where no pressure is applied, is described. The communication of the lymphatic vessels of the pulp with those of the periodontal membrane and the path of the mass down the periodontal membrane from the gingival trough, and its entry into the alveolar bone from this situation are demonstrated, and the way in which the mass reaches the pulp, dentine, and cementum of the tooth from the gingival tissues is discussed.

The significance of various concentrations of the mass in the tissues, particularly the dentine, is also discussed. Control experiments are described, the conclusions which have been reached are given, and the lines on which further experiments are being continued are indicated.

Finally, the application of the results to the pathology of infection in this region, particularly paradontal disease, is given, and also their application to the phenomena of injection anæsthesia.