in the human visceral pleura is the sole reliable criterion for the statement that it belongs to the 'thick type', while all observed animals have a 'thin' type VP. The mesothelium and underlying structures of the SM represent a highly permeable bidirectional membrane with signi?cant differences in the organ and region tra- port as a local phenomenon after horseradish peroxidase application. Stomata are constant features seen by SEM, but are occasional ?ndings observed by TEM over both sides of the diaphragm, lower intercostal spaces, anterior abdominal wall and greater omentum in untreated...