142 On the Origin of the Puhnonary Arteries in Mammals 



each other, and instead of remaining without branches (except those 

 developed later in the lungs) send out buds, each toward the other 

 artery. Fig. 4, x, y. This bending toward the median line of these two 



Fig. 7. Pig of 12.0 mm. Transverse series No. 5, 

 sections 366-404, X 80 diameters. 



Fig. S. Pig- of 12.0 mm. 

 diameters. 



Frontal series No. 6, sections 429-464. X SO 



pulmonary arteries is perhaps caused by the great growth of the auricles 

 of the heart in the pig. Both processes continue until in a pig of 

 9 mm. there is at least one connection between the right and left pul- 



