THE ABDOMEN 899 



the sinus pocularis, or uterus masculinus, which is appended to the prostatic 

 portion of the urethra. 



The Mullerian ducts on the cephaHc side of their fusion form the Fallopian 

 tubes, and the cephaUc extremity of each Mullerian duct, wiiich remains in 

 communication with the coelom. or body -cavity, constitutes the infundibulum, 

 or pavilion, of the corresponding Fallopian tube, in the centre of which in- 

 fundibulum the ostium abdomlnale of the tube is situated. 



The abnormal condition of the uterus known as uterus bicornis is brought 

 about by the fact that the two Mullerian ducts have united at a more posterior 

 (caudal) level than they usually do. The condition known as uterus unicornis 

 is due to imperfect development of one or other Miillerian duct. In extremely 

 rare cases the Mullerian ducts fail to unite, and, by opening independently 

 into the uro-genital sinus, they give rise to a double uterus and a double vagina. 



Structure of the Urethra. 



The wall of the urethra is composed of three coats — muscular, 

 vascular, and mucoue. The muscular coat, which is continuous 

 with that of the bladder, is composed of plain muscuiar tissue, 

 arranged as an outer circular and an inner longitudinal layer. 

 The circular fibres are well developed, especially at the upper end, 

 where they partake somewhat of the nature of a sphincter muscle. 

 Superficial to the circular fibres the urethra, as it lies between the 

 two layers of the triangular ligament, is embraced by the striated 

 fibres of the compressor urethrae. The vascular coat is composed 

 of a rich plexus of veins, supported and pervaded by areolar and 

 elastic tissues. This plexus is continuous above with that around 

 the neck of the bladder. The mucous coat is covered by transi- 

 tional epithelium in its upper part, and stratified squamous epithelium 

 in its lower part. It is provided with papillae, and is thro\sTi into 

 longitudinal folds, which are temporary above, but permanent below. 

 One fold, situated on the posterior wall, is larger than the others, 

 and is known as the crest. The mucous membrane is furnished 

 with tubular mucous glands, and between the permanent folds in 

 the lower part there are crypts or lacimae. 



Lymphatics. — The IjTuphatic vessels of the female urethra join 

 those of the bladder, which pass to the external iliac, internal iliac, 

 and common iliac glands. 



Development of the Urethra. — The female urethra is developed from the 

 anterior or cephalic part of the ventral or uro-genital compartment of the 

 cloaca, which also gives rise to the bladder. It represents the prostatic 

 portion of the male urethra as low cis the sinus pocularis or uterus masculinus. 



The Articulations of the Pelvis. 



Lumbo-sacral Articulation. — The union between the fifth lumbar 

 vertebra and the base of the sacrum is effected by means of the 

 following ligaments : an intervertebral disc, prolongations of the 

 anterior and posterior common ligaments of the bodies of the verte- 

 brae above, capsular ligaments and synovial membranes for the 

 articular processes, ligamenta subflava for the laminae, and inter- 

 spinous and supraspinous ligaments for the spinous processes. 

 These are similar to the corresponding ligaments above the level 



