Joseph Marshall Flint 51 
of the adjacent elements of the same series. Following is a tabulation 
of the branches of a tree in an embryo 18.5 mm. long. 
TRACHEA. 
Iyale 
(2) ID e 
(3) D-L. 
(2) VS. 
(3) DS-LI. 
Right bronchus. Left bronchus. 
Ta 2. Ibe 74 
(2) VI. 
(2) DI. (2) Ap. 
(3) D-L. 
(2) LI. (2) ia. 
(3) DI-S-DS. (3) DS-VI. 
V. 2. 
(A) ik 
(2) VS. 
(2)) VE. 
ID KA IDE Ze 
(2) MW. 
iby By 1 3s 
(2) D.: (2) D. 
(2) VS. 
(Cire 
Wer3 Wiss 
Das: DFS: 
(2) M. (2) M. 
ae Ae L. 4. 
Gav: (Cave 
(2) DS. 
D. 4 D. 4 
V.4 vV.4 
1G. & 15 15) 
1D), 5) D.5 
V.5 Wotd 
L. 6 
Owing to the increasing complexity of the tree, it becomes almost 
impossible to reconstruct it by Born’s method after this stage. At the 
same time I have not succeeded in getting good celluloid corrosions 
younger than 4 cm. pigs. This gap, however, has been partially bridged 
by drawings of the serial sections of the lung of a 23 mm. pig, aided 
by specimens cleared in oil of cloves, or injected and subsequently 
cleared according to the suggestion of Hochstetter, 98. By these methods, 
it is possible to follow the main divisions of the ramifications consider- 
