Joseph Marshall Flint 117 
its presence on both.sides than its absence. The unpaired Lateral 1 
on the right side must be regarded as the normal condition for mammalia, 
due to a phylogenetic provision for the descent of the heart and great 
vessels through the suppression of the element on the left side. In cases 
where it is formed bilaterally, no instance of a left Lateral 1 on the 
trachea has yet been described. As Narath shows, it is always some- 
what lower on the left side than the right when the element is bilaterally 
present. From Narath’s tables, the bronchus is unpaired on the right 
side in 199 species, is bilateral in 15 species, and is absent on both sides 
regularly in 3 species. These three types, apparently, obey no definite 
law ; in the same order of animals, all three types may be found in nearly 
related species. 
In some instances, Lateral 1 arises from the trachea, in others from 
the stem bronchus. When, however, we observe the conditions in those 
animals where it is formed on the trachea, we find the bifurcation occurs 
near the second pair of lateral bronchi. On the other hand, where 
Lateral 1 is produced on the stem, the division of the trachea takes 
place high up, throwing it on to the main bronchus. Its dorsal char- 
acter, in which Narath believes, is, however, secondary, as its lower 
branches are forced backwards by the presence of L. 2 below it and the 
relatively free space beside the vertebral column just above the dorsal 
bronchi. 
APICAL BRONCHUS OF WILLACH AND NARATH. 
So general is the acceptance of the view that Narath is the author of 
this idea, it may be well to quote his own words in which he gives the 
eredit to Willach: “Ich bin ganz der Meinung Willach’s, dass der 
apicale Bronchus ursprunglich ein Seitenast des 1. ventralbronchus sei, 
der auf den Stammbronchus geriickt ist.” Willach explains himself 
thus: “Man konnte also den von Aeby als eparteriell bezeichneten 
Bronchus als Nebenbronchus zum ersten Ventralen derselben Seite im 
Sinne Aeby’s auffassen, der, wenn bronchial, an den Stammbronchus, 
wenn tracheal, an die Trachea abgegeben worden ist.” Further, he says: 
“Andrerseits diirfte aber der erste ventral Seitenbronchus der linken 
Seiten dem der rechten plus dem eparteriellen Bronchus entsprechen. 
Der erste linke ventralbronchus zeigt nimlich einen nach yvorwarts stre- 
benden Ast, der in seiner Gestalt nicht allein Aenlichkeit aufweist mit 
dem eparteriellen Bronchus bei verschiedenen Thieren; sondern er ist 
auch geradezu in einem eparteriellen Gebiet gelegen, wenn man von einem 
ahnlichen, aber doch etwas verainderten Gesichtspunkte aus, als es Aeby 
