The development of the lungs
American Journal of Anatomy
accordance with our modern ideas on the development of the lungs are the papers of Rathke, 28, and Seessel, 77, while more recent contributions are those of Fischelis, 85, and Kastschenko, 87. The work of the latter has been especially emphasized by Wcber and Buvignier, 03, who support his views on the serial homology of the lungs with the braneliiaI pouches. T'hPy believe, from their work on the duck, that in birds as well a d mammals the anlage of the lungs are paired derivatives of the
... atives of the respiratory tube. The lungs, theref ore, while not representing actually existing branchial pouches, indicate the reappearance of entlotlermic evaginations of the head gut which has carried gills among the ancestors of vertebrates. The study of the development of the amphibian and reptilian lung mas taken up somewhat later when Rathkc, 39, in Coluber natrix described its appearance from paired projections from the head gut. He states that the rj,& lung increases in size until it is larger than the stomach while the left remains, in consequence of regressive changes, as a slight appendix of the trachea. Baumann, 02, in Tropidonotus natrix confirms these observations of Rathlre by finding ihe right lung is three times larger than the left in an embryo 3 mm. long, while at 5 mni. it is some forty times larger. But he is inclined to believe, however, that the discrepancy in size is due to arrested development of the left lung sac rather than a true regressive process. Hetrachians were studied by Xemak, 55, who found the first rudiments as paired buds from the head gut passing laterally and caudally, while Gotte, 75, describes the origin of the lungs in hnura from endodermal projections immediately behind the last branchial pouch. Giitte, in Rnura, suggested the possibility of transformed branchial pouches taking part in the formation of the lungs, before Kastschenko described the origin of the avian lung from the respiratory tube. Naturally, the observations of Gotte, like those of Kastschenko, are supported by Weher and Buvignier, 03, while GGtte, 04, himself, more recently reaffirms that theory. Greil, 05, however, who also worked on Anurans comes to the opposite conclusion from these investigators. Primitively the lungs appear, according to Greil, in the form of two bilaterally symmetrical grooves in the ventral wall of the heat gut about the time the first four gill pouches are formed. The fifth and sixth pouches appear later and are separated from the lung anlage by an appreciable space which is greater than the interval between the individual pouches. H e concludes, therefore, that the gill pouches have nothing whatever to do with the formation of the lungs. Jn subsequent stages the pulmonary grooves ileepen and are covered with a thickened splanchnopleure to form the primitive lung sac. L. 2. L. 2. ( 2 ) DI. ( 2 ) AP. (2) vx.