MR. ADDISON ON THE AIR-CELLS OF THE LUNGS. 
161 
ing the mercury onward, these beaded branches became more and more numerous, 
smaller ones proceeding not only from the extremities of those first seen, but shoot- 
ing out from them laterally in all directions ; by continuing a little gentle pressure, 
all symmetrical arrangement was lost in a mass of minute globules (c). These 
beaded branches evidently combine the character both of cells and passages ; each 
bead or globular inflation is an air-cell, communicating with others on either side in 
such manner as to form branched passages *. 
If the pleura be stripped off from the lung of a foetal Calf, the lobules may be 
readily separated from each other, and their subdivisions are carried to a great ex- 
tent. I have measured several from to -^th of an inch only. The smallness of 
the ultimate lobular subdivisions may also be seen by removing a small strip from 
the thin margin of a lung, and slightly compressing it between two slips of glass, 
figs. 5 and 6. 
The lobules have an irregular polygonal figure of from four to six sides : after re- 
spiration the sides are flatter, and the angles sharpened by the pressure of the adjoin- 
ing lobules. 
Experiment 5. — I poured mercury into the lungs of a foetal Calf by the trachea, 
* Reisseissen was the first who noticed the globular distentions or nodules formed on the extreme bronchial 
branches when a lung is injected with mercury ; but he appears to have looked upon them as unnatural or ab- 
normal, produced by the weight of the metal, not considering that the weight or pressure of the air rushing 
into a foetal lung is much greater than the weight of any column of mercury that would usually be employed 
to inject a lung. Speaking of a lobule injected with mercury, he observes, “ Haec fabrica clarius etiamnum per- 
spicietur, lobulo ejusmodi intra duas laminas vitreas comprehenso, ac microscopio subjecto. Laminae autem 
quadamtenus sunt comprimendae ut hydrargyrum, ab aere intus residuo usque repulsum extremos in fines impel- 
latur. Sic apparebit, canaliculos ad extremum usque marginem certo quodam ordine, eoque constantissime servato 
in ramulos excurrere, horumque diametros ad rationem procedentis ramificationis decrescere, ipsam vero in ra- 
mulos divisionem ad finem adeo increbrescere, ut ex singulis cujusque ramuli locis novi circumquaque prove- 
niant, qui, hydrargyro impleti, quasi nodulos referunt ; denique extremos illorum fines tam breves evadere, ut 
speciem tantum globulorum dimidiatorum exhibeant instar brassicae botrytidos stipatorum. 
“ Ne quis autem objicere posset, partes per se tenerrimas hydrargyri pondere extendi, idque ipsum, in globulos 
discedere valde pronum, illusionibus opticis occasionem dare, aliud institui experimentum, quod, quum tales prae- 
cidat dubitationes, viarum spiritalium fines clarius etiam armato oculo repraesentat. Statui itaque illas spiritu 
tantum impletas, nec ulla adhibita vi novo examini submittere. Pulmonem vero quam recentissimum, eumque 
teneriori ex animali exemptum (vitulinus opinor optimus est) aquae submergi deindeque seponi jussi. Turn, 
sublatum post aliquot dies, quum demisso spiritu maxima quidem ex parte collapsus est, nonnulli tamen lobuli 
aerem inclusum etiamnum retinerent, calida curavi perfundendum, sic ut rarefacto per calorem spiritu, distenti 
ramuli in subjecta rubicunda bullarum collapsarum massa facile adspectui se praeberent. Deinde, aeris columella 
scalpelli ope extremos ad fines promota, eandem vidi, ut antea distributionem, praeterquam quod canaliculi minus 
intenti cylindros exactiores referebant. Evidentissime autem cognosci potest, canaliculos ad extremum pro- 
ductos caecos in fines, sive vesiculas pulmonales abire, lobulo tali intra lamellas vitreas microscopio ita subjecto, 
ut a spectro reflexorio pelluceat, et illis subinde leviter agitatis, aer modo antrorsum, modo laterales in ramos 
impellatur. Neque tandem vesicularum forma fallere quenquam potest, pro distentis sacculis illas habentem, 
vel bullulis globosis, quae extremis canalibus sint adnexae, quum ambitum ipsarum ad ramulos, unde prodeunt 
relatum, perinde se habere, atque ramos ad truncum clarissime perspiciat. 
“ Hcec experimenta abunde, ut videtur, ostendunt, vias pulmonum spiritales canales teretes esse ad finem ccecos, mem- 
bramceos, ex tunica videlicet trachece mucosa conformatos, aeri, ut supra commemoratum est, plane impermeabiles.’' 
MDCCCXLTI. 
V 
