102 The Development of the Lungs 
submucous lymphatic plexus is seen in the stem bronchi. It may, how- 
ever, be found earlier, but the vessels are difficult to follow in unin- 
jected specimens. 
It would seem, thus, that we have in the pig’s lung, besides the lym- 
phatic plexuses accompanying the bronchi, arteries and veins, an inter- 
lobular system which Miller has been unable to find in the human lung. 
Injections pointing to such a relationship he has interpreted as arte- 
facts. If Miller’s conclusions prove to be correct, then the lymphatics 
of the human lung must develop so far as the interlobular septa are 
concerned in some other way. 
In following the organogenesis of the lungs in the pig, one finds at no 
period in their life history, openings, or fenestre, which suggest a com- 
munication between adjacent respiratory units. They form, as we have 
seen, independently at the growing ends of the tree and as they approxi- 
mate each other, it is always possible to demonstrate the interlobular or 
interalveolar framework without interruptions suggestive of fenestrae 
offering a communication between adjacent alveoh. Furthermore, in all 
my corrosions, many of which are complete enough to fill completely the 
Alveoli pulmonis and maintain the entire form of the lungs, no instance 
was found of an interalveolar communication. Ruptures frequently 
occur forming irregular extravasations, but in the most complete injec- 
tions, one is always able to isolate completely the individual Lobuli 
respiratoru. The results of this paper, then, support the conclusions of 
Miller, Laguesse, and Oppel, and are not in accord with the views of 
Hansemann, Zimmermann, Merkel, and Schulze with reference to the 
presence of these foramina in the walls of the alveoli of the mammahan 
lung. 
DISCUSSION OF THE LITERATURE. 
THE ANLAGE OF THE LUNGS. 
As in the case of the early stages of the amphibian and reptilian lung, 
there is a general agreement among most authors who have worked upon 
the mammalian lung that the respiratory apparatus arises from an un- 
paired anlage, which the majority regard as asymmetrical. Of these 
investigators, His thinks the future asymmetry of the lungs is to be 
sought in this characteristic of the anlage, while Minot looks upon the 
asymmetry of both anlage and lungs as secondary to changes taking place 
at this time in the heart. Fol believes the anlage is paired and regards 
it, moreover, like Gétte and Weber and Buvignier as associated with the © 
gill pouches. The anlage, in the pig, arises from the ventral portion of 
