Joseph Marshall Flint 121 
being included in the Lobus inferior. In his investigations on the 
human lung, His, from its size, the position of its origin, and its pre- 
cocious development looks upon the Bronchus cardiacus as an inde- 
pendent element which appears out of the regular schematic order, a 
view with which Willach agrees. Robinson, while accepting the onto- 
genetic interpretation of His, believes with Aeby in its phylogenetic 
derivation from the Lateral 2. In holding that it may arise either from 
the second lateral or the stem bronchus, Zumstein takes a combined 
view, that is to say, in some instances it is an accessory bronchus and in 
others it is an independent structure. Narath is a most decided sup- 
porter of Aeby’s doctrine, both from an embryological and a comparative 
point of view, but thinks L. 3 and L. 4, as well as the second lateral 
bronchus may give rise to this trunk, a view in which he is supported 
by Merkel and Blisnianskaja. d’Hardiviller and Nicholas and Dimi- 
trova, however, look upon it as one of the principal branches of the stem 
bronchus. In the pig, the independence of this element is shown with 
great clearness where it forms the largest element of the ventral group 
of bronchi. Its hyperdevelopment apparently results from the increase 
in the respiratory surface by the utilization of the space between the heart 
and liver medialwards to the two stem bronchi for lung tissue. It is 
unpaired, like Lateral 1 and with that element destroys the symmetry 
of the tree. 
MEDIAL BRONCHI. 
Aeby’s idea in classifying this group as dorsoaccessory, that is to say, 
branches originating on the dorsal bronchi and wandering on to the 
stem bronchus was practically the same as in the case of his ventro- 
accessory group, namely, their inconstancy and the existence, in a 
series of adult lungs, of bronchi, which looked like transition stages 
between the origin of a medial element on a dorsal trunk and its final 
position on the stem bronchus. Willach, without definite observations, 
supported this view, while Robinson, who calls them dorsointernal 
bronchi and believes them accessory, in the sense of Aeby, describes their 
origin by means of a splitting of the division between the two buds of a 
dorsal bronchus down to the main bronchus leaving the inner one of the 
buds with an independent origin on the stem. Zumstein speaks of them 
as medial and independent in which he has the support of Nicholas and 
Dimitrova and d’Hardiviller, although the latter designates the group 
as an internal series. Merkel accepts the older doctrine of Aeby. 
Narath, also, believes from both embryological grounds and from com- 
