. The American journal of anatomy. apropria. Here and there, where capillaries project into the lumen of theair passages, the nucleus lies in the angle formed by the capillary and thebasement membrane with the protoplasmic portion of the cell projectingup over the capillary, like a non-nucleated plate. Adjacent Lobuli respiratorii impinge on each other, pressing the looseconnective tissue, which has hitherto existed between the lobules into athin membrane in which the capillaries run. This interalveolar mem-brane now consists of the membrana propria of the adjacent lobules, to-gether with the
. The American journal of anatomy. apropria. Here and there, where capillaries project into the lumen of theair passages, the nucleus lies in the angle formed by the capillary and thebasement membrane with the protoplasmic portion of the cell projectingup over the capillary, like a non-nucleated plate. Adjacent Lobuli respiratorii impinge on each other, pressing the looseconnective tissue, which has hitherto existed between the lobules into athin membrane in which the capillaries run. This interalveolar mem-brane now consists of the membrana propria of the adjacent lobules, to-gether with the interalveolar connective tissue. The lymphatics in thevarious parts of the lung still show essentially the same relationships. After birth (Fig. 29) the development of the lung has advanced along 98 The Development of the Lungs the same lines followed in embryonic life. The chief changes occur inthe resiDiratory lobules. The bronchiolus (Fig. 29 b) is clothed bycubical epithelium surrounded by a well-marked basement membrane y^^-^. Text Fig. 29. Sections of a portion of the lobule of the lung of a pig, tv/odays old. Same preparation as used with tissue shown in Fig. 28. X ^ lymphatics, ft = bronchiolus. br = bronchiolus respiratorius. i = duc-tulus alveolaris. a ^ atria, srt = sacculi alveolares. c ^ alveoli pulmonaris. Joseph Marshall Flint 99 about which are numerous connective-tissue cells. There is as yet, how-ever, no differentiation of this layer into nmscle fibers. From this arisethe short Bronchioli respiratorii (Fig. 39 hr) where the cubical epithe-lium flattens as the passages run into the Ductuli alveolares (Fig. 29i).From these structures, the Atria (Fig. 29 a) are formed, which in turnproduce the Sacculi alveolares (Fig. 29 sa). The air sacs which wereonly indicated in a pig 27 cm. long are now distinctly seen. It is pos-sible that they are even more developed before birth than is shown inFig. 28, as I have frequently found embryos in utero 29 cm.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectanatomy, bookyear1901
