494 
motory nerves are almost exclusively found 
here. The tubules of the sympathetic nerves 
are chiefly given to the proper mucous metm- 
branes and to the glands. All these will be 
considered more at length under other heads, 
and they are therefore only referred to here. 
Of the arevlar tissue —Before describing 
the remarkable varieties presented by this 
tissue under different parts of the mucous 
system, I must advert to its constitution in 
Ose situations where its ordinary characters 
are well marked—as in subcutaneous fascia, 
in muscle, on the exterior of the pharynx, &c. 
Singular as it may appear, there is no correct 
account of this structure in any of the works on 
minute anatomy. [tin truth consists of two 
tissues, distinct from each other, and respec- 
tively allied to the white and to the yellow 
fibrous tissues. The white fibrous element of 
areolur tissue is chiefly in the form of bands of 
very unequal thickness, in which are to be 
seen numerous streaks taking the general direc- 
tion of the whole, but not parallel to the border, 
nor continuous from end to end. These streaks 
more resemble the creases of a longitudinal 
folding than intervals between separate fibrille, 
for which they have been mistaken. These 
bands split up without difficulty in the long 
direction, whence result fibrils of the most va- 
ried width, the finest being far too minute for 
measurement, even with the best instruments.* 
These bands interlace and cross one another in 
various directions, and their natural course is 
wavy. They frequently subdivide and join 
those near them. [esides these bands, com- 
monly called fasciculi, there are some finer 
filaments of the utmost tenuity which seem to 
take an uncertain course among the rest. The 
yellow fibrous element is everywhere in the 
form of solitary fibrilla, which correspond in 
their essential characters with the tissue of that 
name. They are disposed to curl, and are 
traly branched at intervals of variable length ; 
these branches (which usually retain the size of 
the fibril from which they spring) becoming 
continuous with others in the neighbourhood. 
They have higher refractive properties than the 
white element, and their borders are conse- 
quently darker. 
It is easy to overlook this twofold compo- 
sition of areolar tissue in specimens examined 
in water, but their discrimination is made easy 
by a trifling artifice. This consists in adding a 
drop of acetic acid, which instantly swells the 
white bands, and makes them transparent, but 
produces no change in the yellow fibrils. These 
effects of tle acid may be watched, if the agent 
be made tospread gradually over the specimen ; 
and there can scarcely be conceived a more 
beautiful example of the aid chemistry will 
afford anatomy than that presented in the 
course of this interesting process.t The change 
* The fibrille of true white fibrous tissue are 
almost precisely similar, and, as I believe, are only 
produced by he observer himself in opening out 
his specimen for inspection. 
+ In the case of the dartos, this procedure de- 
tects not only what has just been described, but a 
third element, hitherto in this situation quite con- 
MUCOUS MEMBRANE, 
produced in the white bands is such as to shew — 
very clearly that they are not truly fasciculi, or 
aggregations of fibrille. The action of the 
acid on these two elements is identical with 
that produced on the two tissues to which I~ 
have shewn them to be anatomically allied. 
To these two elements of areolar tissue are 
be attributed physical properties similar to the 
of white and yellow fibrous tissues, and 
will vary greatly in different situations, accord 
ing to the proportion and mode of arrangement 
under which the two elements coexist. 
Of the arcolar tissue of glands.—The 
appears to be a very prevalent misconception 
with to the quantity of this 
found in the interior of the large glands, as 
liver and kidney. It is imagined that it p 
trates into every interstice, mingles with 
capillary rete, and envelopes the ultimate 
secreting tubules. It is, however, impossible 
in the most recent specimen of these organs 
to discover anything answering to this deserip-— 
tion. All that can usually be detected is a 
small quantity accompanying the larger vessels 
in their course within the organ, and forming 
septa between its coarse subdivisions. And it 
would be difficult to suppose a purpose which 
more abundant supply could subserve. The ca- 
pillary network mo Y the secreting tubules by their 
mutual and intricate interlacement sufficiently 
sustain one another; no freedom of motion is 
required between them; there is no fore 
tending to separate them. I am far from 
saying, however, that the ultimate substance ¢ 
these glands consists only of simple mucoi 
membrane and bloodvessels. In the inter- 
stices of these there are probably nerves a 
lymphatics, of the mode of termination 
which we know nothing, but which seem much 
fewer than is commonly supposed. There 
also more or less of an interstitial amorphou 
substance, hereafter to be described, - a 
In these glands and in the substance of” 
many compound mucous membranes there are 
to be seen here and there small bodies up 
unlike cellular tissue in an early stage of 1 
development. They have a bulging nue! 
from which they taper to the extremities; ai 
they are much longer and slenderer than 
prismatic epithelium. With their nature a 
use I am at present quite unacquainted. 
The lungs seem mainly to owe their extrao 
nary elasticity to the yellow fibrous element 
their submucous areolar tissue. This is spre 
in great abundance under the whole 
and much predominates over the white. Int 
trachea ef bronchia it is besides largely ¢ 
loped in longitudinal bands visible through 
mucous membrane. In the whole of this 
gion its fibrils take a general longitudinal d 
tion, but branch and inosculate at very freq 
intervals, enclosing areole of small dimensi 
But this element does not cease with the tut 
it is prolonged in the form of branching, are! 
bands over the basement membrane of the @ 
cells, which it renders elastic and firmly suppor 
founded with areolar tissue. This is non-strial 
muscle, at once known by its beiny loaded wi 
coipuscles, v1 persistent cell-nuclei. See MUSC 
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