Joseph Marshall Flint 37 
in size. At the same time, Lateral 1, the tracheal bronchus (PI. I, Figs. 
13, 14, L. 1) has grown further lateralwards. Its terminal bud beyond 
the constriction near the point of origin bends somewhat ventralwards 
in conformation to the topography of the environment of the thoracic 
cavity at this level. Its general course after its origin is dorsalwards 
causing its lower extremity to overlap the upper part of L. 2 (Pl. I, 
Figs. 13, 14, L. 2). The asymmetrical characteristics of the two-stem 
bronchi are also maintained, the right extending lower and nearer the 
midline than the left, which projects more lateralwards. They also bend 
slightly dorsalwards. It is probable, however, that the asymmetry of this 
specimen is extreme, as I possess other specimens at this age in which 
the two sides, while markedly asymmetrical, are more nearly enanteo- 
morphic than this one. In order to control this specimen, it was re- 
constructed a second time with exactly the same results. Of the two 
second lateral bronchi (Pl. I, Figs. 13, 14, L. 2), the right extends a 
little farther lateralwards and ventralwards than the left, its growth 
being influenced at this stage by the presence of L. 1 above and behind 
it. The left, however, with practically unobstructed environment grows 
lateralwards and dorsalwards and upwards at this period. Both are 
terminated by the end buds, which lke that on L. 1, are in a stage pre- 
paratory to division. On the right side, Ventral 2 (Pl. I, Fig. 13, V. 2) 
the Bronchus infracardiacus has developed to a button-like bud on the 
ventral portion of the stem bronchus separated from it by a sharp con- 
striction at the base. It is not so well developed as the two second 
lateral bronchi or L. 1. On the corresponding portion of the left stem 
bronchus, no analogous branch has appeared. It remains, in fact, naked 
through the whole future development of the tree. Neither is there in 
the pig, at this or later stages, a branch which forms at this point and 
subsequently wanders up on left L. 2, as d’Hardiviller suggests, to form 
the so-called cardiac bronchus of Hasse. On the lateral sides of both 
stem bronchi, buds forming Lateral 3 (Pl. I, Figs. 13, 14, L. 3) have ap- 
peared. These extend directly lateralwards for a short distance to termi- 
nate in swollen bud-like extremities, while the portion near the stem 
bronchus has a definite constriction. Of the two, the right is shghtly larger 
than the left. From this point on, the stem bronchus continues caudal- 
wards to terminate in the enlarged end buds. On the right side, the axial 
bronchus extends considerably lower than on the left. On the dorsal 
side of the stem between L. 2 and L. 3, appears on each side, the bud 
representing Dorsal 2 (Pl. I, Fig. 14, D. 2). That on the right side ap- 
pears before the left and is a trifle more developed. The left, however, is 
quite apparent. It is also possible that either of these buds may not be 
