URETHRA. 



1251 



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 ab.sent. The bloodvessels from the spongy 

 body shoot through it. This contractile tissue 

 is identical with that recently described by 

 Kolliker 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, anil 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 

 Kolliker 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 Kolliker 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 gallinaginis 

 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 vesica;, 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, follows, 

 secondly a strong layer of yellowish circular, 

 fibres of muscular and elastic tissue. This 

 layer is connected above with the sphincter 

 vesicoe, 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 

 fibres. 



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, in small numbers, 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 

 0-1 of a line long, from 1'002 to 0'003 wide. 

 They contain small nuclei from 0'012 to O'Ol-i 

 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 

 urethra? (corpus spongiosum), since they have 

 no venous spaces between them, but rather 

 form a continuous membrane, which limits 

 the corpus cavernosum urethra towards 

 the mucous membrane. One might con- 

 sider this part as belonging to the corpus 

 cavernosum urethras ; in which point of view 



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