RESPIRATORY SPACES OF THE LUNGS one 
In the septa the delicate elastic fibers run an irregular course. 
The elastic fibers in the muscle bundles of the free edges of the 
septa present the same picture as that described in Rana nigro- 
maculata. 
2. Klastic fibers in Reptilia and Aves 
Clemmys japonicus. We can distinguish, according to ar- 
rangement, the same two layers of elastic fibers as in Rana and 
Megalobatrachus. The nets of fibers are sligtly looser than 
those in Diemyctylus. In the muscle bundles in the edges of 
the septa the elastic fibers are especially abundant on the surface, 
contrasting to the looser structure in the muscle bundle. 
Gecko japonicus. The elastic fibers in this animal are found 
only on the surfaces of the muscle bundles. 
Elaphe quadrivirgata. The elastic fibers in the connective 
tissue in the outer wall of the lung are mainly longitudinal. 
Among these fibers are interspersed elastic strands which are 
somewhat coarser. We have also the fibers which accompany 
the muscle bundles. In the septa the elastic fibers are seen almost 
exclusively in relation to the muscle bundles. The fibers accom- 
panying the muscle bundles are remarkably coarse, more so than 
in other localities in this animal, and even coarser than the 
fibers described in the preceding animals. 
Aves. Eberth has not recognized any elastic fibers in the 
alveoli (respiratory canaliculi), while Schulze states their existence. 
The domestic fowl was studied and elastic fibers were not found 
in the respiratory canaliculi, but were seen accompanying the 
muscle bundles around the flute-holes. In the pigeon lung a 
parcel of elastic fibers is found in the part of the respiratory 
canaliculi nearest the flute holes. 
3. Elastic fibers in Mammalia 
For investigation of elastic tissue in mammalian material 
thick sections are essential. The conventional celloidin em- 
bedding method cannot be used because the dyes employed also 
stain the celloidin, giving a dark background. Thus frozen and 
