Bauhaus-Universität Weimar

The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Todd, Robert Bentley
varies in depth in different parts, and is thicker 
in the membranous than in other parts of the 
urethra. When examined with the micro¬ 
scope, it presents abundant evidence of the 
existence of contractile fibre mixed with com¬ 
mon elastic tissue. The relative quantity of 
these elements varies according to situation : 
thus, in the membranous portion, there is less 
of the contractile tissue than in the spongy 
portion ; a circumstance of some interest, as, 
this part being surrounded by a distinct mus¬ 
cular covering, there would be less necessity 
for it than in other situations where muscle 
is absent. The bloodvessels from the spongy 
body shoot through it. This contractile tissue 
is identical with that recently described by 
Kölliker as entering into the structure of the 
spleen and mucous canals, which have an 
evidently contractile power. 
The existence of this layer has been long 
recognised, and the attention of anatomists 
was directed specially to it by Sir E. Home, 
who believed it to be muscular; and his 
opinion was supported by the observations 
of Mr. Wilson, who attributes the resist¬ 
ance occasionally, in irritable states of the 
urethra, offered to the introduction of the 
catheter, and the expulsion of bougies in like 
conditions, to spasm of these supposed mus¬ 
cular fibres. This idea, however, was opposed 
by Sir Charles Bell ; but the dispute is de¬ 
prived of its interest since the discovery by 
Kölliker of the true nature of this peculiar 
tissue, which combines to a certain extent the 
attributes of organic muscular fibre and elastic 
tissue. This layer varies in depth in different 
subjects, and is generally highly developed in 
the robust and muscular, so as in some in¬ 
dividuals to grasp with considerable firmness 
a bougie when introduced into the canal. 
Wilson mentions an instance of a gentleman 
who could “as distinctly feel a contraction 
of the passage coming on, and taking place at 
one part, as he could feel any muscle act.” 
The use of this layer must necessarily be to 
regulate the force of the current of fluids 
through the urethra. 
According to Kölliker the following is the 
arrangement of the submucous layer in various 
parts °of the urethra. It is termed by him 
the simple muscular tissue. “ Its relations 
are most complicated in the prostate gland, 
and the prostatic portion of the urethra, 
which is rich in muscular fibres. So large is 
the quantity of this tissue in the gland itself, 
that the true glandular structure constitutes 
scarcely one third or one fourth of the whole. 
On removing the mucous membrane from the 
prostatic portion of the urethra, the yellow 
longitudinal fibres of the caput gallmagims 
come first into view, which form the lower 
end of the trigone, and contain very few mus¬ 
cular fibres. On both sides of the caput gal- 
linaginis, and extending to the anterior wall 
of the urethra, similar yellowish longitudinal 
fibres present themselves, and form a strong 
layer towards the neck of the bladder; but 
towards the membranous part of the urethra 
they gradually decrease to a very delicate 
layer. This longitudinal fibrous layer of the 
prostatic part is connected, internally to the 
sphincter vesicæ, by a thin and indistinct layer 
of fibres with some of the longitudinal mus¬ 
cular fibres of the bladder ; but by far the 
greater part of it is unconnected with this 
latter : it consists of half fibro-cellular tissue 
with many nucleus-fibres, and half of evident, 
smooth, muscular fibres with characteristic 
nuclei. After this, and external to it, follow's, 
secondly a strong layer of yellowish circular, 
fibres of muscular and elastic tissue. This 
layer is connected above with the sphincter 
vesicæ, where also it is most developed ; whilst 
below it becomes gradually thinner, and below 
the caput gallinaginis is either lost, or appears 
only in very small quantities. On removing 
the several muscular layers, we come at last 
to the proper glandular tissue of the prostate, 
of which individual lobes penetrate among 
the circular fibres just mentioned, their ex¬ 
cretory ducts passing through the longitudinal 
In the membranous part of the urethra the 
smooth muscular tissue is less developed. 
Under the mucous membrane, whose cellular 
tissue is remarkable for abundance of elastic 
fibres, there is a layer of longitudinal fibres, 
which are connected with those of the pro¬ 
static portion. These fibres consist for the 
most part of fibro-cellular tissue with nucleus- 
fibres, and include,insmallnumbers, undulating, 
delicate, and curved contracting fibre-cells (of 
the nature of smooth muscular fibres), which 
may be, in part, isolated ; and are from 0*07 to 
0T of a line long, from U002 to 0'003 wide. 
They contain small nuclei from 0'012 to 0-014 
long, and are more easily found in recent 
specimens than in those treated with acetic 
acid. External to these longitudinal fibres 
there is a strong layer of transverse fibres, 
which belong for the most part to the mus- 
culus urethralis. Some of these, however, 
especially those belonging to the inner layer, 
display some strong bundles of smooth mus¬ 
cular fibres, together with fibro-cellular tissue 
and nucleus-fibres, and a partial mixture of 
fasciculi of the transversely striated fibres of 
the musculus urethralis. 
The smooth muscular fibres are generally 
still less developed in the spongy portion of 
the urethra. In some cases they appear in 
exactly the same manner as the longitudinal 
fibres in the membranous portion ; in other 
cases, longitudinal fibres may be seen, but no 
muscular tissue can be found mingled with 
the cellular tissue and nucleus-fibres of which 
they consist. At a certain depth, however 
some longitudinal fibres are distinguishable, 
with a more or less considerable admixture 
of smooth muscle, which fibres cannot be re¬ 
garded as beams of the corpus cavernosum 
urethrae (corpus spongiosum), since they have 
no venous spaces between them, but rather 
form a continuous membrane, which limits 
the corpus cavernosum urethrae towards 
the mucous membrane. One might con¬ 
sider this part as belonging to the corpus 
cavernosum urethrae ; in which point of view 
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