CONSTRICTOR URETHRA MUSCLE. 



265 



meets with its fellow of the opposite side behind the bulb, at the central 

 point of the perinseum. Its fibres conceal Cowper's gland. 



The constrictor urethrcc muscle consists of a number of transverse fibres 

 extending across the arch of the pubis, some of them above and others 

 below the membranous portion of the urethra, and closely embracing it. In 

 some bodies a tendinous raphe, placed over the middle of the urinary canal, 

 separates each stratum into lateral halves. 



This muscle rests in contact with the deep layer of the triangular ligament, which 

 separates it from the anterior fibres of the levator ani. 



The transverse constrictor of the urethra was known to Santorini. One of the 

 representations of it, contained in his posthumous work, has been copied for the 

 woodcut (Fig. 204). Indistinctly or partially noticed by other anatomists, the 

 muscle was first fully described by Guthrie ; and the whole of the muscular structure 

 connected with the membranous part of the urethra was examined about the same 

 time by Mliller, but the results were not published till a later period. (Guthrie, 

 "Anatomy and Disease of the Neck of the Bladder," &c., 1834; Johannes Miiller, 

 " Ueber die organischen N erven der erectilen mannlichen Geschlechts-Organe/' &c. 

 1836.) 



Fig. 204. 



Fig. 204. POSTERIOR VIEW OP THE PUBES, 



WITH PART OP THE BLADDER AND 



URETHRA ATTACHED (from Sautorini). 



1, body ; 2, rami of the pubes ; 3, 

 obturator interims muscle ; 5, poi'tion of 

 the fundus and neck of the bladder laid 

 open ; 6, the prostate gland ; 7, trans- 

 verse fibres of the compressor urethrse 

 muscle, passing above the urethra; 8, 

 similar fibres passing beneath that canal. 



Circular fibres of Santorini (stra- 

 tum internum circulare, Miiller). 

 Beneath the transverse muscle just 

 described is a series of circular in- 

 voluntary muscular fibres, entirely 

 surrounding the membranous part 

 of the urethra : these are continuous 

 behind with the circular fibres of 

 the prostate, and are referred to in 

 the description of that body. (See Structure of the Prostate. ) 



A pubo-urethral muscle was described by James Wilson (Medico-Chirurgical Trans., 

 London, vol. i. p. 176), and is sometimes referred to as Wilson's muscle, but has not 

 been recognised as a separate muscle by succeeding anatomists who have given 

 special attention to the subject of the muscular structures round the urethra. An 

 unstriped pubo-vesical band has been described, descending from the back of the sym- 

 physis to the neck of the bladder (Luschka). 



B. IN THE FEMALE. 



In the female the anterior fibres of the levator ani embrace the vagina as 

 they do the prostate in the male. 



The transversus perincei and the sphincter ani are arranged nearly in the 

 same manner as in the male. 



