183 
best preserved in a mixture of equal parts of glycerine, alchohol and 
water. 
Direct modeling I found of great service in the study of small 
corrosions of the tips of the bronchi of embryos. For the more com- 
plex lungs the reconstruction method of Born was at last resorted to, 
by which after the devotion of nearly two years to a single specimen, 
the desired light was obtained. — The lung was first prepared by 
making a triple injection by which the capillaries were filled with 
Prussian blue — the arteries with vermillion — and the veins with 
ultramarine-blue-gelatine. A single lobule was then removed, imbedded 
in paraffine and cut into sections 20 w thick. The magnifying power 
employed in reconstruction was one hundred, and each section was 
drawn on a wax plate two millimetres thick. As long as the terminal 
bronchus is in the section it is quite easy to locate all the air cells 
from section to section. Beyond the terminal bronchus the location 
of the blood-vessels and the shape of the air sacs served as guides. 
In this way all the air cells communicating with one bronchus were 
drawn on wax plates and the sections carefully cut out. The frame- 
work left, when piled up, gave an exact model of the air sacs, and 
the pieces piled gave a „corrosion“ of the same. The models were 
now cut in various directions in order to study the relation of the 
air sacs to the terminal bronchus. 
Although my study is from the comparative standpoint, the pre- 
sent preliminary communication is confined wholly to the dog’s lung. 
Lung-lobule. 
As Arpy*) has well said: „Von einem dichotomischen Zerfalle 
der beiden Luftröhrenäste ist nirgends die Rede.“ I have thus far 
been unable to discover any regularity in their distribution. The last 
division of the bronchus before breaking up into the parenchyma of 
the lung, is known as the terminal bronchus and from this arise 
a number of passages which widen out into an expansion. From this 
other passages lead out which upon into a central cavity set about 
with small irregular cells. A good idea of this arrangement may be 
obtained if we compare it to a Pompeian house. The passage leading 
off from the terminal bronchus is the „vestibulum“, which opens into 
the „atrium“. From this arises the ,,faux‘, or air-sac passage, which 
leads into the ,,peristylum“ or air-sac. This air-sac is set about with 
„eubicula“ or air-cells. 
1) Der Bronchialbaum der Säugetiere und des Menschen, Leipzig 
1880, p. 3. 
