I89 8 HUMAN ANATOMY. 



vessels from these several sources anastomose and produce a net-work that encloses 

 the canal and sends twigs that break up into capillaries that supply the coats com- 

 posing its wall. The z'efns begin within the mucosa beneath which they form a in- 

 ternal plexus that communicates with a wider-meshed outer plexus within the fibrous 

 coat, from which tributaries pass to the internal or common iliac and the spermatic 

 veins The lymphatics within the mucous membrane and submucosa, according to 

 Sakata ' are not demonstrable as distinct net-works, but as such are seen wtiMto the 

 muscular tissue and on the surface. The lymph-trunks from the middle third of the 

 ureter, which are the most numerous, pass to the lumbar nodes ; those from the lower 

 segment are tributary to the internal iliac nodes or communicate with the lymphatics 

 of the bladder ; while those of the upper part either empty into the aortic noc 

 join the renal lymphatics. 



The nerves of the renal duct, derived from the sympathetic system, accompany 

 the arteries and come from the renal, spermatic, and hypogastric plexuses Within 

 the adventitia they form a plexus containing numerous microscopic ganglia, the largest 

 of which are at the upper and lower ends of the duct. In addition to the fibres sup- 

 plying the blood-vessels, both medullated and non-medullated fibres pass to the mus- 

 cular and mucous coats. 



Variations These consist most often in more or less complete doubling of the canal on 

 one or both sides. While subdivision of the pelvis into an unusual number of tubular calyces 

 is rare, its cleavage into two separate compartments, either alone or in correspondence with 

 doubling of the ureter, is relatively common. The division may be so complete that the two 

 resulting ducts open into the bladder by separate orifices. The termination of the ureter in 

 the seminal vesicle a malformation occasionally encountered depends upon the close embryo- 

 logical relations (page 2039) which exist between the two structures. While congenital absence 

 oMhe kidney is not necessarily associated with entire absence of the ureter, failure of the 

 latter to develop implies incompleteness or absence of the kidney, since a part of the duct- 

 system of the latter is derived from the primitive ureter (page 1937). 



PRACTICAL CONSIDERATIONS: THE URETERS. 



The ureters may be multiple from a fused kidney, or two or more ureters may 

 spring from the pelvis of a single kidney, indicating a defect in the development of 

 the primary foetal ureter. The separate ureters may unite at any point between the 

 kidney and the bladder or may remain distinct throughout. 



Marked obliquity of insertion of the ureter into the pelvis (page 1896) may 

 Irave on a lower level than the ureteral origin a pouch of the pelvis corresponding 

 to the lowest of its original subdivisions which, when it fills with urine, compresses 

 the upper end of the ureter, narrows its lumen, and favors the production of hydro- 

 nephrosis. This condition may also occur in either the second or third of the fol- 

 lowing variations in the upper end of the ureter thus described by Hyrtl : (a) there 

 is IH> pelvis, but the ureter divides into two branches without dilatation at the point 

 of division, each branch having a calibre a little larger than that of the ureter ; () 

 there is a pelvis, that is, a funnel-shaped dilatation at the point of division ; the 

 upper portion is the smaller, and terminates in three short calyces; the lower and 

 more voluminous portion terminates in four or five calyces ; (c) there is only half a 

 pelvis, that is, the lower branch divides and is funnel-shaped, forming a narrow 

 pelvis, which terminates in one, two, or three short calyces; while the upper is not 

 dilated, and extends to the upper portion of the kidney as a continuation of the 

 ureter (Fenger). 



The lower end of the ureter may in the male, as a rare anomaly, open within 

 the boundaries of the sphincter vesicae, or into the prostatic urethra, or into the 

 seminal \-oirK-. ejaculatorv duct, <>r vas deferens. 



As the opening is never anterior to the compressor urethras, incontinence of 

 urii; ^ult. but interference with its free exit causes ureteral dilatation and 



lu'lronephrosis. 



In the female the ureter may open into the urethra, vagina, or vestibule. 

 There mav l>e incontinence of urine, or again such obstruction as to cause uretero- 

 renal dilat ition. 



1 Archiv f. Anat. u. KnUvick., 1903. 



