122 The Development of the Lungs 
parative anatomy that these bronchi can be traced as branches of the 
dorsal group. A criticism of his view has already been given. In the 
pig, they are irregular, but independent products of the stem. As they 
never occur more than a short distance above L. 4, we find the reason lies 
in the presence of the cesophagus, which prevents the development of 
medial bronchi above that level. 
The main results of the preceding paper may be expressed in the fol- 
lowing: 
Résumé. 
1. The anlage of the lungs in the pig is unpaired and asymmetrical. 
It arises from the ventral part of the head gut behind the Sinus venosus, 
as a ventral outgrowth, preceded by a lateral flattening of the foregut 
below the gill pouches and the appearance of longitudinal furrows, which 
divide the fore gut into two parts, a ventral respiratory portion and a dor- 
sal digestive segment. From the lower part of the anlage the lungs arise, 
from the upper the trachea. If there is a serial phylogenetic association 
between the pulmonary anlage and the gill pouches, as some authors 
maintain, the connection is lost in the pig, for the lungs originate well 
below the gill area and distinctly ventralwards to the series of bronchial 
pouches. From the caudal extremity of the pulmonary anlage, arise 
two lateral outgrowths, giving rise to the stem bronchi. These, like the 
anlage itself, are asymmetrical, the right growing lateralwards and 
caudalwards, while the left extends almost directly horizontal. Then 
the respiratory and digestive portions begin to separate, a process, which 
begins from the caudal end of the anlage and extends upwards along the 
line formed by the two longitudinal furrows, freeing the respiratory 
apparatus from the cesophagus. In its subsequent growth, the pulmo- 
nary anlage enlarges, the tips of the stem bronchi dilate, and begin to 
bend dorsalwards around the cesophagus. ‘This results in the formation 
of the primitive lung sacs. At this time, the production of the bronchi 
begins. They are readily divided into four series from the topography 
of their origin, namely, lateral, dorsal, ventral, and medial. 
2. The first lateral bronchus, the so-called “ eparterial bronchus,” is, 
in the pig, unpaired and arises as a lateral outgrowth from the right 
side of the trachea, just above the roots of the two stem bronchi. It 
is distinctly lateral in origin and bears a serial relationship to the re- 
mainder of the lateral bronchi. Its position in mammals varies, some- 
times it is on the stem bronchus, but it is often situated on the trachea. 
