364 CHIKANOSUKE OGAWA 
time they multiply by cell division. To my regret, I could not 
confirm this by mitotic figures in the alveolar walls of the lungs 
which were injected with water and stained with ordinary dyes. 
MUSCLE FIBERS 
1. Muscle fibers in Amphibia 
Diemyctylus pyrrhogaster. Miller demonstrated in the lung 
of Triton a muscle layer in which the whole lung was almost 
entirely enclosed. ‘These muscle fibers are well developed in the 
Triton cristatus, but much less so in the Triton taeniatus. Ac- 
cording to his statement, the fibers run circularly, crossing some- 
what here and there and are located between the capillaries and 
weak connective tissue which cover the lung. Oppel observed 
that the muscle layer of Triton alpestris consists of circularly 
arranged muscle cells which are often grouped. In Diemyc- 
tylus pyrrhogaster the muscle fibers are for the most part circu- 
lar; occasionally longitudinal fibers are intermingled with them. 
The muscle fibers in Diemyctylus do not appear in groups, which 
is contrary to Oppel’s statement. They have interwoven with 
their substance elastic and collagenous fibers. 
Rana nigromaculata. Concerning the lung of Rana, Gaupp has 
already made detailed statement, which is as follows: ‘The 
smooth muscle tissue, which represents essential foundation of 
the lung wall and septa, form finer and coarser bundles, which 
make a firm framework, connecting with each other. The 
strongest, thickest of these muscle bundles lie in the free, thick- 
ened edges of the chief septa, the muscle bundles in the septa of 
the secondary order are correspondingly thinner. From these 
principal bundles of the edges of the septathinner fibers originate, 
which go down in the septa and connect with the finer muscle 
bundles of the outer lung wall.’ According to my finding in 
Rana nigromaculata, I can distinguish two systems of muscle 
fibers in the outer lung wall. One forms relatively strong bun- 
dles, the other consists some irregularly arranged fibers. In the 
septa the muscle fibers appear in bundles, and in no instance do 
they seem to appear singly. The muscle bundles in the edges 
