[Distribution of the lymph vessels in the mouse heart. A light and electron microscopic study (author's transl)].

The lymphatic system in normal mouse heart was investigated by light and electron microscopy. Lymph vessels were only demonstrated in the subepicardial layer and the outer half of the myocardium. Here above all they were situated in close vicinity to arteries and thin-walled veins, rarely separated in the interstitial space, never in the subendocardial layer of the left ventricular wall. The myocardium contains only 2 lymph vessels per mm2. By means of electron microscopy all lymph vessels were regarded as lymph capillaries. Their ultrastructure is described in detail. This investigation shows that lymph vessels in normal heart are rarer than supposeed till now. It is possible that most of the ultrafiltrated fluid is drained by the cardiac venous system, while the lymphatic system only has to transport a small amount of protein-rich fluid.