RESPIRATORY SPACES OF THE LUNGS 343 
It is to be concluded from the conditions resulting from 
silver impregnation that these nuclei belong to the epithelial 
cells and not to the subjacent tissue. 
The large, flat cells cover either the intercapillary spaces alone 
or both the capillaries and the intercapillary spaces; sometimes 
a cell lies over several intercapillary spaces at the same time. 
The arrangement of the respiratory epithelium is not uniform 
in the different 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 lined by groups of 
numerous small cells. It is only in these regions that I can 
confirm Elenz’s statement. Most of the epithelial tissue is 
different, in that for the most part the small cells are isolated, 
and when they do form groups, these consist of only a few cells, 
rarely of a large number. ‘The flat cells therefore occupy the 
greater part of the field and often cover the interecapillary spaces 
also. It is possible that the difference between Elenz’s observa- 
tions and mine can be accounted for by the fact that he studied 
the structure of only a part of the lung and believed it to be 
representative of the whole. 
Gecko japonicus. Up to this time, no account seems to have 
been given of the respiratory epithelium of Gecko. 
Just as in the tortoise, the tissue consists of two kinds of epi- 
thelial cells (fig. 7). The intercapillary spaces are of the same 
width as those of the tortoise and two or three times as wide as 
the diameter of the capillaries. The two layers of the capillary 
network of each septum do not directly communicate with each 
other. 
The small cells are of various shapes, sometimes more or less 
flattened, sometimes irregularly rounded, elliptical, elongated, 
square, or pentagonal, and approximately twice as large as those 
of Clemmys and Elaphe. The cell borders are not straight, 
but curve inward more or less; even if one border is relatively 
straight, others are generally curved. The angles of the cell 
borders are often obtuse. The small cells are found either 
isolated or in groups. When they are found singly, each one 
covers either a small intercapillary space completely or a wider 
