RESPIRATORY SPACES OF THE LUNGS 389 
alveolar pores, it is not known whether this result was due either 
to actual lack of pores because of individual discrepancy or to 
the fact that only a few pores were present and not shown in 
the sections studied. It was difficult to determine quantitatively 
the relation between age and alveolar pores because the exact 
ages of the investigated animals were not known. 
In conclusion, the relation of elastic and reticular fibers to the 
alveolar pores will be considered. These fibers around the 
alveolar pores are sometimes present and sometimes absent; 
when present, the fibers either wholly or partially enclose the 
pore, and these fibers are sometimes relatively thick and some- 
times thin. Linser’s statement that there are mostly elastic 
fibers around the alveolar pores was not confirmed. 
SUMMARY 
1. The respiratory epithelium in Amphibia is of one kind and 
consists of flat and nucleated portions, while in Reptilia the 
epithelium consists of two kinds of cells, namely, large, flat cells 
and small cells, both being nucleated. Thus the respiratory 
epithelium of Reptilia takes the middle form of those of Amphibia 
and Mammalia. 
2. The arrangement of the respiratory epithelium of Elaphe 
quadrivirgata (snake) is different in parts of the lung. The 
intercapillary spaces near the caudal sac-like portion and of the 
parts on both sides of the median line of the dorsal aspect are 
covered by groups of numerous small cells, while in most part 
the small cells are isolated or form groups of a few cells. . 
The small cells of respiratory epithelium of Gecko often present, 
singly or in groups, crescent or horseshoe form and are located 
eccentrically in the intercapillary spaces against the capillaries. 
3. The respiratory epithelium seems to be absent in birds. 
It is also the case in the mole and bat. However the inter- 
capillary spaces of the lung of the young mole and those of a 
part of alveolar bases, which are in contact with the pleura, in 
the lung of the adult mole are covered by nucleated cells. 
4, Lange’s experimental work concerning respiratory epithe- 
lium has some fundamental mistakes. 
