RESPIRATORY SPACES OF THE LUNGS BET! 
undeveloped state as shown by their weak staining and that 
immediately after parturition they become developed. Otto- 
lenghi says that the degree of staining of the elastic fibers is of 
value in forensic medicine. He finds that the fibers in the lung 
of a still-born fetus, which died after a few breaths of air showed 
much darker staining than those of a fetus before parturition. 
He concluded that this sudden change in staining was due to 
the contact of the elastic fibers with air. 
I recognize also that the elastic fibers in the embryonic lung 
are stained weakly, but in addition it was observed that the 
elastic fiber rings of the alveolar ducts and alveoli were stained 
somewhat deeper than the fibers of the alveolar walls. Also 
it is seen that the elastic fibers in the respiratory spaces of the 
embryonic lung are in general not stretched and present a wind- 
ing course, while if such lungs were expanded by a fixing solution, 
the elastic fibers are stretched as in the adult lung. In my com- 
parison of the degree of staining of the elastic fibers of the mature 
embryo and the new-born, I was unable to confirm the differences 
described by Ottolenghi. 
RETICULAR FIBERS 
The reticular fibers have been studied rather by workers in 
pathology and somewhat neglected by histologists, though Mall 
has given detailed statements about them. ‘This is true espe- 
cially in the lung, notwithstanding the great importance of these 
fibers as the supporting tissue. No research seems to have been 
made in other vertebrates than the human, where Russakoff has 
studied these fibers in the lung. 
The Bielschowsky method was used in the investigation. 
Both formol and formol alcohol were used in fixing, and the latter 
was found as effective as the former. The tannin-silver method 
was tried, but the results were poor, owing to some undetermined 
cause. 
In Diemyctylus the lung was cut open and spread out, in the 
other Amphibia the septa were removed with scissors, these un- 
sectioned specimens were stained, but with no success. This 
