Joseph Marshall Flint 3 
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 Weber and Buvignier, 03, who support 
his views on the serial homology of the lungs with the branchial 
pouches. They believe, from their work on the duck, that in birds as 
well as mammals the anlage of the lungs are paired derivatives of the 
respiratory tube. The lungs, therefore, while not representing actually 
existing branchial pouches, indicate the reappearance of endodermic 
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 
was taken up somewhat later when Rathke, 39, in Coluber natrix de- 
scribed its appearance from paired projections from the head gut. He 
states that’ the right 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, o2, in Tropidonotus natrix 
confirms these observations of Rathke by finding the right lung is three 
times larger than the left in an embryo 3 mm. long, while at 5 mm. 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. Betrachians were studied by 
Remak, 55, who found the first rudiments as paired buds from the 
head gut passing laterally and caudally, while Gétte, 75, describes 
the origin of the lungs in Anura from endodermal projections imme- 
diately behind the last branchial pouch. Gé6tte, in Anura, 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 Weber and Buvig- 
nier, 03, while Gétte, 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, ac- 
cording 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. He concludes, therefore, that 
the gill pouches have nothing whatever to do with the formation of 
the lungs. In subsequent stages the pulmonary grooves deepen and are 
covered with a thickened splanchnopleure to form the primitive lung sac. 
