John Lewis Bremer 



141 



vertebrates with lungs the laulmonary arteries originate one from each 

 pulmonary arch, and "that Rathke's diagrams, though describing per- 

 fectly the adult and late embryonic conditions, are, as regards this origin, 

 incorrect. 



In the pig, one of the animals examined by Rathke, although the 

 symmetrical origin is preserved, one pulmonary artery arising from each 

 pulmonary arch, and although the ultimate appearance, that of both 



Fig. 5. 



Fig. 6. 



Fig. 5. Pig of 9.0 mm. Frontal series No. 54, sections 462-502. X 80 

 diameters. 



Fig. 6. Pig of 11.0 mm. Sagittal series No. 8, sections 96-113. X 80 

 diameters. 



pulmonary arteries arising from the mid-point of the left pulmonary 

 arch, is the same as in the other mammals I have examined, the inter- 

 mediate steps are different, as is shown in Figs. 4 to 9. Instead of 

 remaining comparatively parallel, as in the rabbit, the pulmonary ar- 

 teries, after attaining considerable length (pig of 7.8 mm.), bend toward 



