MR. ADDISON ON THE AIR-CELLS OF THE LUNGS. 
159 
nently occupied by air-bubbles, in the mass of which all trace of the symmetry 
of their branched arrangement is entirely lost or obscured. The rounded inflations 
of one branch meeting on all sides those of the adjoining branches, are moulded by 
pressure into pentagonal or hexagonal forms, which are the figures of the air-cells, 
fig. 9. 
Branched passages, however, still exist, and form a communication between the 
cells ; but these passages are now neither tubular nor cylindrical. It is therefore 
necessary to distinguish them, and I have called them Lobular Passages, an appro- 
priate term suggested to me by Dr. R. B. Todd. 
The air-cells have not an indiscriminate and general intercommunication through- 
out the interior of a lobule. I have before observed that there are no anastomoses 
between the intralobular bronchial ramifications ; hence the air-cells formed along 
the branch (b), fig. 8, do not communicate with those in the branch (c), except by 
means of their common opening into a larger branch at ( d ), and so on for each 
branch respectively. 
Experiment 1. — Take a very thin section of inflated and dried lung, and submit it 
to an examination by the microscope. A great number of large and well-defined 
Oval Foramina, ( a , a) fig. 1, with a sharp and delicate edge, will be seen thickly dis- 
tributed among the cells. Frequently three, four, or five of them ( b , b) may be seen 
close together, and whichever way the section be made, they are equally numerous 
and conspicuous. These foramina are evidently not portions of bronchial tubes, 
for they have no uniform cylindrical wall, which is necessary to constitute a tube. 
By gently altering the focus of the microscope you may look down through the upper- 
most foramina into the interior of air-cells situated laterally below them, and several 
foramina and cells may thus be brought successively into view (c, c). 
These foramina are portions of the lobular passages, and if the section be taken from 
the surface of the lung, including the pleura, they are smaller, and placed at more 
equal distances from each other, than when made from the interior of the organ, 
fig. 2 ; which is exactly the result that would accrue from a division of branched 
passages, in the former case (fig. 2.) approaching their terminations, and in the latter 
(fig. 1.) nearer the point whence the branches emanate. 
Experiment 2. — I injected with mercury a small bronchial tube in the lung of an Ox, 
leading towards the thin margin of the organ ; the metal appeared at the surface, 
forming a mass of minute globules. Having made an incision in the interval between 
two lobules and inflated the cellular tissue, I was enabled carefully to dissect away 
the pleura, and I then observed through a lens that the globules were contained in 
delicate membranous sacs, forming rounded eminences projecting from the tissue. I 
then separated several lobules from each other, and saw the mercury at the surface 
of every lobule, presenting rounded eminences similar to those observed at the surface 
of the lung. On examining these rounded eminences or globules in the microscope, 
I perceived that the mercury was not inclosed in a simple sac or cell, but in a divided 
