The states described here are those characterized by failure of the lymphatics to fulfil their function of draining the tissues of fluid which the blood capillaries are unable to accept. This failure may be due to an inherent defect in the lymphatic system, to an acquired organic blockage or to a disorder, once functional, which has become organic. Excluded from consideration are the nutritional edemas, the nephritic edemas, the cardiac edemas and the edemas of pregnancy; in short, all that are related to general or constitutional, as opposed to local, causes.
The tissue fluid is of course derived from blood. Such of it as is composed of water and salts reenters the blood capillaries, but plasma proteins and foreign material are unable to do so. Material of this sort and, in general, all substances whose contact with the body cells might harm the organism must, then, be carried off by