160 
MR. ADDISON ON THE AIR-CELLS OF THE LUNGS. 
or multilocular cavity. Nor is it difficult to comprehend the character of these mul- 
tilocular cells at the surface, when we conceive the nature of the structure of a lobule, 
consisting of numberless small branches of a ramified tube, which the atmosphere at 
birth distends into cells. The extremities of these branches, evolving or shooting forth 
under the pressure of the air, meet with resistance and support from the adjoining 
lobules, and being as it were thrown back upon themselves, form the multilocular 
cavities or cells I have described ( b , c') fig. 8. Wagner’s figure represents these ter- 
minal cells only*. 
Experiment 3. — Having inflated a recent lung, I cut off a small portion, and ex- 
amined it as an opake object by the microscope ; I found all the oval foramina occu- 
pied by large air- bubbles, other bubbles of various sizes occupying the surrounding 
cells. I then placed a very small piece between two slips of glass, which were so 
arranged under the microscope that I could gently and gradually press them together, 
still keeping the object {now viewed transparent) in focus. I then observed the air- 
bubbles changing their situation, not by moving equably through any tube or cylin- 
drical passage, but by sudden starts from cell to cell. I frequently saw a large 
bubble of air become compressed for a moment in passing from one cell to another, 
and sometimes divide into two smaller bubbles, one of which passed on to another 
cell, the other retiring to the spot from which a momentary pressure had removed it. 
I have frequently watched a bubble of air pass through three or four cells in succes- 
sion, the communication between them not being through a tubular passage, but by 
limited openings (oval foramina) leading from cell to cell. 
It does occasionally happen that a small portion of bronchial tube may be included 
in the object thus submitted to examination, and if so, when the glasses are pressed 
together, the air-bubbles glide easily and readily through it. The bubbles of air 
formed in the lungs are of all dimensions, some large, some small, and others so 
minute as not to measure more than x oVo th or -g^th °f an inch in diameter ; hence 
three, four or more may occupy a single cell, and the heterogeneous adhesion be- 
tween them and the tissue is so strong, that it is impossible to expel all of them by 
pressure. They may, however, be removed from very thin sections of recent lung by 
two or three days’ maceration in water, and the pulmonary network is by this means 
rendered very distinct ; and if such sections be carefully examined by a lens, lobular 
passages may be seen partially laid open, disclosing a series of communicating cells 
{a, a, b, fig. 3.). 
Experiment 4. — If the lungs of a Rabbit be allowed to macerate for two or three 
days, all the air-bubbles at the thin edge of the organ will be removed, and this por- 
tion assimilated to a foetal state. Having prepared a lung in this way, I poured 
mercury into the trachea, and allowed the metal by its own weight to traverse the 
air-tubes and passages ; it appeared at the surface of some of the lobules in the form 
of little globules {a, fig. 4.), in others as beaded or nodulated branches ( b .). By press- 
* leones Physiologicse, tab. xv. fig. 8, 1839. 
