82 The Development of the Lungs 
base of the heart beyond the midline making the sum of lung tissue in 
L. 1 and L. 2 considerably greater than that in L. 2 on the opposite side. 
Owing to this growth, the Lobus medius is pressed ventralwards, its 
dorsal segment lying in the angle between the Lobus superior and the 
Lobus inferior. It may be interesting to note, that the portion of the 
Abiae Ine, 7A0), 
Text Fic. 20. Outline drawings of the lungs of a pig 19 cm. long. 
A. Right side. B. Left side. C. Diaphragmatic surface. At this stage, the 
surface of the lungs is smooth. The topography of the bronchi beneath, 
taken from corrosion specimens of the same age, is indicated by dotted lines 
and letters. 
lobe which lies in this angle, is supplied by the large dorsoinferior 
bronchus. It is, therefore, ontogenetically equivalent (vide Pl. II, 
Figs. 15, 16) to the apical segment of the Lobus superior on the other 
side. Nothing could indicate clearer the adaptation of the growing 
