272 



zwar prinzipiell in ganz ähnlicher Weise, wie bei den letzteren. Inso- 

 fern wiederholt sich auch in der Ontogenese des Kienienapparates der 

 Wirbeltiere die phylogenetische Entwickelung, um in jenen an der 

 Körperoberfläche sich ausbreitenden Kiemenformen, die von manchen 

 wohl ohne jegliche Berechtigung als primitive Zustände betrachtet 

 wurden, ihr Extrem zu erreichen. 



Meran, September 1905. (Eingegangen am 20. Oktober.) 



Nachdruck verboten. 



The Growth of the Bronchial Tree. 



Preliminary Note. 



By Joseph Marshall Flint, M. D., 

 Professor of Anatomj'' in the University of California. 



In selecting material for the study of the development of the 

 lung in mammals, I was governed, in choosing the pig, partly by the 

 richness of the available material, but largely by the fact that this 

 lung possesses in well developed form, not only all groups of bronchi^ 

 but particularly the most discussed types, namely, a tracheal bronchus 

 and the so-called "accessory groups". In the process of its growth 

 from the pulmonary anläge, the bronchial tree of the pig produces 

 four sets of branches, all of which, with one exception, originate from 

 the stem bronchus. During the formation of the primitive lung sacs, 

 after the production of the right and left bronchi and the separation 

 of the trachea from the head gut is complete, one observes im embryos 

 about 7,5 — 8 mm in length nape-breech measurement, a lateral evagin- 

 ation from the wall of the trachea a short distance above the origin 

 of the two chief bronchi. This occurs only on the right side and 

 represents the first lateral bronchus. It is the "eparterial bronchus" 

 of Aeby and the "apical bronchus" of Narath. Although in its 

 topography, it lies behind the pulmonary artery there is no evidence 

 to show that the artery has anything to do with its formation. In the 

 pig, this is an unpaired element, but in certain other animals it is 

 often present on both sides, situated either on the trachea or the stem 

 bronchus. As it represents an element of the lateral series, despite 

 its asymmetry and its topographical relationship to the pulmoray 

 artery, I have termed it. Lateral 1. The reasons for this choice I 

 shall give in a later paper, where the growth of the tree will be 

 described in detail. While this bronchus is in the process of form- 



