MUCOUS MEMBRANE: 
passages, as formerly described, the submu- 
cous areolar tissue presents a remarkable mo- 
dification, and is closely joined to the peri- 
chondrium of the inner surface of the cartilages. 
It is worthy of remark that the glands with 
which the tracheal portion of the membrane is 
furnished, are not placed, like the buccal, 
duodenal, and other similar glands, immedi- 
ately subjacent to the mucous membrane, but 
on the posterior surface of the trachealis muscle, 
which is pierced by their ducts. This peculiar 
arrangement would seem to be accounted for 
by the deviation from the ordinary form which 
the submucous areolar tissue here presents, 
and which renders it ill adapted to give to these 
irregular-shaped bodies that loose investment 
which they everywhere possess, and which 
therefore appears necessary to them. 
The mucous lining of the whole alimentary 
canal below the cardia is the largest and best 
marked example cf what I have termed the 
compound mucous membrane, being com- 
_ posed of vertical tubes which are truly glands, 
_ Opening on the general surface. ‘That of the 
_ small intestine presents villi also. This entire 
membrane is very soft and easily torn, because 
its chief mass consists of an epithelium, the 
particles of which adhere but slightly either to 
one another or to the basement membrane, and 
are everywhere disposed in a single layer. 
There is moreover scarcely any areolar tissue 
between its involutions, which have, therefore, 
little besides the vascular web to sustain them. 
The submucous areolar tissue is in considerable 
abundance between the mucous and the muscular 
coats. (See Sromacu and InrestinaLCawnat.) 
The lining membrane of the hepatic and pan- 
creatic ducts is simple, and its epithelium of the 
prismatic variety. 
In the genito-urinary tract, the epithelium 
resents every variety. The fossa navicularis* 
is clothed with small, flat, or roundish scales, 
_ the rest of the urethra with a single series of 
' prismatic particles. The cells of the prostate 
| are lined with spheroidal epithelium, the vasa 
_ deferentia with prisms. In the vesicule semi- 
nales there is a pavement of somewhat flat- 
tened granules, and also in Cowper’s glands. 
In the bladder, ureters, and pelves of the kid- 
-neys, the epithelium is in the form of longish 
cells intermediate between the spheroidal and 
the prismatic varieties. The aymphe, clitoris, 
hymen, and vagina are covered with scaly epi- 
thelium, and this has been noticed by Henle in 
cases where the*hymen has been entire. Within 
| the neck of the uterus the epitheliuin becomes 
_ prismatic and clothed with cilia, and so con- 
_ tinues over the surface of the uterus and Fal- 
lopian tubes, and even for some distance over 
__ the outer surface of their fimbriated extremities. 
eyond this it merges gradually into the com- 
essed cells of the serous membrane. The 
_ lining membrane of the Fallopian tubes, as well 
_ as that of the uterus, is of a compound nature, 
especially during gestation, and consists of 
ules arranged vertically to the general sur- 
e. It is to be observed that the cilia only 
* Henle, loc. cit. 
) VOL. III. 
497 
clothe the general surface, and that the epithe- 
lium lining the tubules is spheroidal, or inter- 
mediate between that and the prismatic. It isa 
form of the glandular variety, and bears no cilia. 
Of the glands——The varieties apparent in 
these organs also may be explained by an ex- 
amination of the modifications and modes of 
aggregation of the elementary tissues already 
mentioned. It may be said, in general terms, 
that the glands are characterized by their solid 
form, by the great preponderance of their epi- 
thelial and vascular tissues, and by the small 
quantity of their areolar tissue. It is rare for 
this last to invest every individual involution 
of the mucous surface in the interior of a gland ; 
but it usually gives a common covering to the 
whole organ, as well as less complete ones to 
those subdivisions of it, termed lobes or lo- 
bules, which result from the mode of distri- 
bution of the bloodvessels and duct, and are 
designed for the purposes of package or pro- 
tection. 
Such an investment is usually termed the 
proper coat or capsule of a gland, and seems 
to correspond most nearly with the submucous 
areolar tissue of the compound mucous mem- 
brane, as, for example, that of the intestinal 
canal. 
The propriety of these remarks will appear, 
on a particular application of them. As I be- 
fore entered somewhat in detail into the internal 
composition of the liver, it may now be se- 
lected for illustration. The epithelium, which 
in the gall-bladder and larger ducts is of the 
prismatic kind, becomes bulky and of a flat- 
tened spheroidal form, in the lobules. It there 
also acquires a peculiar character, viz. nume- 
rous minute globules of an oily or fatty nature, 
disseminated within the substance of each par- 
ticle. The basement tissue seems to cease, 
and on an examination of a thin section of the 
lobule under a high power of the microscope, 
its chief bulk appears to consist of epithelium. 
There is scarcely a trace of areolar tissue to be 
anywhere detected. Even the coats of the 
capacious capillary bloodvessels, in the close 
meshes of which the ultimate ramifications of 
the bile ducts are situated, are with difficulty 
seen, and are of extreme delicacy. The sub- 
mucous areolar tissue of the hepatic ducts, 
with which the whole of the contiguous cap- 
sule of Glisson should be associated, cannot, 
when arrived at the lobules, be followed into 
their interior. It can only be distinguished in 
very slender quantity, giving them a partial in- 
vestment, on those aspects which share in form- 
ing the portal and hepatic-venous canals, and 
where, in the angles of union between three or 
more lobules, a terminal twig of the portal 
vein runs up to open on all sides into their 
capillary plexus. No lobule is isolated from 
the rest by a complete capsule, but commu- 
nicates immediately by its capillary network, 
with those near it. The intralobular vein has 
a similar want of areolar tissue around it; and 
thus the main mass of the lobule, and of the 
whole liver, consists of epithelium and a plexus 
of capillaries. Those lobules, however, whick 
contribute to form the general surface of the 
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