MUCOUS MEMBRANE. 
A portion of a tubrile of the human 
kidney, magnijied -OU diameters, 
Ata, the basement membrane and 
epithelium are both seen in a iy 
natural state. At 6, the base- yl) 
ment membrane has been sepa-_ ff 
rated, and the epithelium is some- 
what s ollen, and its outline 
‘woolly.”? At ¢, the epithelium 
has been detached and the base- 
ment membrane is seen somewhat 
wrinkled: d,a detached epithe- 
lial particle seen in face; its 
minutely mottled texture is not © }) 
represented in the wood-cut. 
most probably the early condition of the new 
or advancing series of these particles. Its 
thickness in the kidney certainly does not ex- 
ceed the sgiggth of an English inch. I have dis- 
covered, that in the Malpighian bodies of the 
kidney, which are the dilated extremities of 
the urmiferous ducts, with an enclosed tuft of 
arterial capillaries, the basement membrare is 
ofien, to some extent, naturally bare, i.e. w.thout 
a covering of epithelium. This is the only situa- 
tion of the body in which such an arrangement 
is known. 
In the testis, the same membrane may be 
shewn without difficulty to be that which gives 
to its secreting tubules their peculiar strength ; 
and here, as might be expected, it is somewhat 
modified. The difference is principally as 
regards its thickness, which here reaches y,4,,th 
of an English inch, and in some animals 
Fig. 274. 
A portion of a tubule of the testis ( Guinea-pig, Co- 
baya), magnijied 300 diumeters. 
a@a, basement membrane; a’, corpuscle in its sub- 
stance ; b 6, epithelium in situ, consisting of par- 
ticles of different dimensions, with minute gra- 
nules in their interstices ; c, cavity of the tubule 
full of detached epithelium particles, of various 
size and appearance, and mingled with nume- 
 rous seminal animalcules; d, one of these semi- 
nal animalcules. 
even exceeds that amount, its essential charac- 
ters, however, remaining the same. In the 
larger tubes, emerging from the gland, this 
tunic becomes gradually invested by a delicate 
fibrous layer, by which the vascu'ar network is 
attached to it, aud which at first sight may 
487 
appear to form an integrant part of the wall 
of the canal. 
Terminal vesicles of the pancreas of the dog, magnified 
300 diameters. 
The basement membrane is seen ata a a, where the 
epithelium has been a little detached. 
In the salivary and all the allied glands, 
the basement membrane admits of being easily 
demonstrated. A very thin slice of the fresh 
organ should be torn by needles, gently washed, 
and inspected under a high power. The termi- 
nal vesicles of the duct will then be brought 
into view and their outline seen to be perfectly 
sharp and linear (fig. 275, a aa). In parts 
where the epithelium which they contain has 
been loosened, the basement membrane will be 
left in relief. It is of extreme delicacy ; and, as 
in all other situations, its capillary plexus (when 
well filled with coloured material) may he seen 
ramifying, not in its substance (for its tenuity 
renders such a disposition impossible), but on 
its parenchymal surface. 
have sought in vain for the basement mem- 
brane in the lobules of the liver, and I am in- 
clined to think that it does not exist in this 
gland, except in the excretory part of the bile 
ducts. 
In the air-cel!s of the lungs the basement 
membrane assumes a most interesting and re- 
markable developement, for it constitutes almost 
the entire thickness of their walls, the epithe- 
lium being of extreme delicacy. It appears to 
be here strengthened by interlacing arches of 
elastic fibrous tissue, but to be itself transpa- 
rent and homogeneous, as elsewhere. It is on 
its parenchymal surface that the close vascular 
web is spread out. (See Putmo.) 
But this membrane may be also detected in 
every part of the alimentary tube, which is 
more characteristically mucous, in that, viz. in- 
tervening between the cardia and the lower ex- 
tremity of the canal. Here it deserves an 
attentive study on account of the apparent com- 
plexity of its foldings, and because its exist- 
ence here offers the most unequivocal proof 
which we possess, of the anatomical identity of 
the true glands with the membranes usually 
called mucous. As it is more delicate in this 
part than any other, and difficult of detection 
by reason of the enormous preponderance of its 
epithelial investment, I shall describe the man- 
ner in which it may be best observed. The 
specimen should be as fresh and healthy as 
possible, or should have been immersed in 
