The structure of the respiratory portion of the mammalian lung with notes on the lining of the frog lung

Abstract

FIVE PLATES (ELEVEN FIGURES)At thc present time the question which concerns most investigators of lung structure is whether there is or is not a continuous cellular epithelial membrane lining the resipratory portion of the mammalian lung. Some workers believe that there is no adequate method for demonstrating the existence of a continuous epithelium lining the pulmonary alveoli in mammalian lungs. Although the silver nitrate method has been the one most extensively used for this purpose, during the past 15 years an increasing number of workers have concluded that it gives diverse and irregular results which have been interpreted fallaciously. Very recently, however, other workers have used solutions of silver nitrate and other silver salts and claim to have confirmed anew the findings of earlier workers who first applied this method to the study of the respiratory portion of the lung.However, among those who maintain, on the basis of silver nitrate studies, that mammalian pulmonary alveoli are lined by a continuous epithelial covering of endodermal origin, there

Pores of Kohn

“…Laguesse (1927) made another relevant observation in reporting that pigmented alveolar phagocytes were found lying in pores apparently passing from one alveolus to another. This observation was confirmed and illustrated by Brodersen (1933), Macklin (1935), Loosli (1937, 1938, Loosli et al (1949), and Schaefer et al (1964). The finding of alveolar macrophages in pores is confirmed in Figures 3 and 5, and further comment by Loosli (1937) that macrophages were sometimes seen lying in two pores at the same time is illustrated in Figure 5, in which a macrophage is seen to by lying around a central capillary column with part of the cell in each half of a divided pore.…”

“…Laguesse (19'27) illustrated a section of lung showing not only three pores but also what he called an epithelial cell engaged in one of the pores presenting separate surfaces to two alveoli. The same observation was made again by Loosli (1937) when he noted the granular vacuolated cytoplasm of some cells he found lying in pores and which he considered to be epithelial. The following year he (Loosli, 1938) considered this cell in greater detail and identified it with what had been originally called the 'small nucleated epithelial cell', renamed by Lang (1925) the 'septal cell' (as he considered it to be of connective tissue origin).…”

“…The same observation was made again by Loosli (1937) when he noted the granular vacuolated cytoplasm of some cells he found lying in pores and which he considered to be epithelial. The following year he (Loosli, 1938) considered this cell in greater detail and identified it with what had been originally called the 'small nucleated epithelial cell', renamed by Lang (1925) the 'septal cell' (as he considered it to be of connective tissue origin). Loosli pointed out that this same cell was variously described by others as 'epicyte' (Clara, 1936), 'pneumocyte' (Businco, 1933), 'pericyte' (Bargmann, 1935), 'histiocyte' (Fried, 1934), and 'vacuolated macrophage' (Robertson and Uhley, 1936).…”

“…On the other hand, Loosli (1937) pointed out that textbooks of histology at that time had little or nothing to say regarding pores. Now, some 30 years later, the situation has not changed.…”

Microscopic Anatomy of the Lower Respiratory Tract of the Grey Short‐Tailed Opossum (Monodelphis domestica)

“…Because of the importance of this region to all species, previous researchers have published articles on the microscopic anatomy of the lower respiratory tract of numerous mammalian species (rodents, carnivores, ovines, porcines, ruminants and non‐human primates) (Clements, 1938; Loosli, 1938; Ham and Baldwin, 1941; Hansell and Moretti, 1969; Greenwood and Holland, 1972; Tucker, 1974; Castleman et al., 1975; Jeffery and Reid, 1975; Becci et al., 1978; Alcorn et al., 1981; Pack et al., 1981; Spicer et al., 1982; Jeffery, 1983; Tyler and Plopper, 1985; Scheuermann et al., 1988; Al‐Tikriti et al., 1991). However, publications on this area in non‐placental mammals have been limited to eight articles during the past century.…”