‘bei ae menl 
M. Flourens on the Structure of Mucous Membranes. 381 
bladder—as the result of pathological derangement. On this occasion, I 
exhibit it isolated—detached from the other membranes by a process 
which is regular, methodical, and certain ; nor do I exhibit the epidermis 
only—I display the three, the epidermis, mucous body, and dermis. 
The mucous membranes, then, have all one and the same fundamental 
structure, which structure is complex. None is simple. All of these, 
however attenuated and delicate they may be, are always possessed of 
three layers or distinct membranes. And this is so universally the case, 
that even the internal Membrane of the Arteries, which some anatomists 
have already classed among the mucous membranes,* supplies the three 
layers or membranes, distinct and superimposed, upon which I am dwelling. 
The specimen No. 5, which I now submit, is a portion of the aorta of the 
ox ; and here the three layers are conspicuous as in the former examples. 
These layers, I now add, can be completely isolated and detached from 
each other by slow maceration, methodically conducted, the only means 
by which it can be effected, and a good illustration of the vast import- 
ance of the kind of process we pursue in investigating anatomical struc- 
ture. Malpighi employed the process of boiling for the purpose of de- 
taching the several layers of mucous membrane from each other, and by 
this process he obtained the mucous net-worx of the tongue. I, on the 
other hand, used a slow and careful maceration, and, instead of a net- 
work, procured a continuous and complete layer. In a former memoir,t 
I have shewn that this famous net-work of Malpighi is entirely a factitious 
one, and that the mucous membrane of the tongue is essentially a continu- 
ous and complete layer. The perforations which transform this continuous 
layer into a net-work are owing to the tearing open of the sheaths, which 
the mucous body supplies to the papillee of the dermis. Each of these 
papillee has, in fact, a double sheath, as I have already shewn ;{ the one 
supplied by the mucous body, and the other by the epidermis. If, then, 
the method of boiling is employed, as was done by Malpighi, the epider- 
mis becomes brittle and contracts. Every one of the sheaths of the mu= 
cous body is thus ruptured and compressed in each sheath of the epider- 
mis; and when, after this, the epidermis is removed, the whole of the 
sheaths of the mucous body are torn and removed. Wherever, then, 
there is naturally a mucous sheath, a vacuity is produced, and the whole 
mucous body, which is normally a continuous layer, now appears a com- 
plete net-work. 
* Bichat, Anat. Gener., t. ii. p. 52. What is the nature of this internal or 
common membrane of arteries? On this point I am in complete ignorance.” 
Beclard again, says, “ The lining membrane has been compared to serous mem- 
brane, and to mucous or cellular tissue ; it may, however, resemble the arachnoid 
membrane,” Elem, d’Anat. Gener., p. 371. Later anatomists, who have com- 
pared them with mucous membranes, have come much nearer the truth, 
Tt Comptes Rendus, vol. iv. p. 445. t Ibid. 
VOL. XXXII. NO. LXIV.— APRIL 1842. ce 
