Observation of the secretion on the surface of the bronchioles with the scanning electron microscope

The secretion covering the surface of the bronchioles can be demonstrated with the scanning electron microscope if fixative is introduced into the pulmonary artery or directly into the lung rather than through the trachea. Buffered glutaraldehyde, ethanol, or an ethanol-ether mixture can be used as a fixative. With this method of preparation the surface secretion appears as a smooth coating covering the cilia and cells. The secretion is insoluble in ethanol ether or chloroform methanol, suggesting that there is little lipid contained in it. Reasons are cited for believing that the major component of the secretion is a protein that arises from the Clara cell.