[Peculiar capillary convolution of the parietal pleura. III. Electron microscopy studies]

By means of electron microscopy and ultrahistochemical research it has been attempted to detail the structure and explain the function of the pleural tufts of the parietal pleura present in the ventral mediastinum of dogs. This led to the discovery that the varions forms present for the surface-enlarging pleura protusions in actuality exhibit corresponding morphological characteristics. As a special formation of the serous lamina of parietal pleura, they are covered by an occasionally incomplete mesothel unit. The parenchyma of these organs is compinsed of a macrophage-rich outer border zone and of a vessel-canying central zone. The experimental in vivo application of cationized ferritin in the pleura-space clearly indicated a high resorptive metabolism of the mesothel and of the pluripotential mesenchym cells. The higher incidence of lymphoplasmatic cell-forms in the proximity of the central vessels along with leucocytic cell infiltrations fulfill an immunocellular and phagocytic function. The structure of the cell population of the pleural tufts partaking on the resorption of matter out of the pleural space has been discussed in detail. The in vivo application of a cationized ferritin solution for the purpose of studying these resorptive processes has been critically judged.