24 The Development of the Lungs 
the work of Moser and Hesser, the student of the mammalian lung, how- 
ever, may look upon its phylogeny as being no longer in conflict with its 
ontogeny, and may also state his problem in the following series of 
questions: 
1. Is the anlage of the lung unpaired or paired? 
2. Is it symmetrical or asymmetrical ? 
3. Does the pulmonary artery exert any fundamental influence upon 
the growth of the bronchial tree, separating it into two regions of un- 
equal significance as expressed in Aeby’s Ep- and Hyparterial theory? 
4. Is the “eparterial bronchus” an independent structure or a de- 
rivation of the 2d lateral bronchus? Is it an unpaired or paired ele- 
ment? Does an “eparterial bronchus” always form on the left side 
and then degenerate or undergo atrophic changes ? 
5. Is the Bronchus ascendens of His, or the left apical bronchus of 
Narath, the equivalent of the ‘‘ eparterial bronchus ” ? 
6. Are the lateral bronchi independent structures ? 
7. Are the dorsal bronchi independent structures or derived from the 
lateral group ? 
8. Are the ventral bronchi independent structures or derived from the 
lateral group ? . 
9. Are the medial bronchi independent or derived from the dorsal 
group? 
10. Is the Bronchus cardiacus an independent or accessory bronchus ? 
11. In what way do the bronchi grow? Does one system of growth 
predominate throughout the whole development of the bronchial tree? 
12. What is equivalent value of the lobes of one lung in terms of the 
other ? 
THe ANLAGE OF THE LUNGS. 
The development of the respiratory apparatus begins in a pig by a 
lateral flattening of the head gut just below the Fundus branchiales. At 
the age represented by an embryo, 3.5 mm. nape breech measurement, 
the last gill pouch has in transsection (Fig. 1)* a flattened rhomboidal 
form with dorsal, ventral, and lateral angles. Below this gill pouch, 
lying behind the Sinus venosus, which already shows evidences of the 
increasing asymmetry of the heart, the ventral angle as it deepens to form 
the pulmonary groove (PI. I, Fig. 1) is pushed somewhat to the right 
of the median plane (Fig. 1). The head gut in passing caudalwards, 
* References to Text-Figures may read simply Fig. 1, or Fig. 2, or Fig. 
3, etc., but every reference to figures on plates is accompanied by the proper 
plate number. 
