852 THE VASCULAR SYSTEM. 
usually terminates by two branches ; behind and above it communicates with the vesical 
plexus, and receives tributaries from the seminal vesicles and vasa deferentia. One or 
more efferent vessels pass from it on each side and open into the corresponding internal 
iliac vein. 
The inferior vesical plexus of the female, which represents the prostatico-vesical 
plexus of the male, surrounds the upper part of the urethra and the neck of the bladder, 
It receives the dorsal vein of the clitoris, and its efferent vessels terminate in the internal 
iliac vein. 
Dorsal Veins of the Penis (vv. dorsales penis).—There are two dorsal veins of 
the penis—the superficial and the deep. 
The superficial dorsal vein receives tributaries from the prepuce, and runs backwards 
immediately beneath the skin to the symphysis, where it divides into two branches which 
terminate in the superficial external pudic veins. 
The deep dorsal vein lies on the dorsum of the penis beneath the deep fascia. It 
commences in the sulcus behind the glans, by the union of numerous tributaries from 
the glans and the anterior parts of the corpora cavernosa, and runs backwards in the mid- 
dorsal line, in the suleus between the corpora cavernosa, from which it receives many 
additional tributaries. At the root of the penis the vein passes between the two layers of 
the suspensory ligament, and then between the subpubic ligament and the deep transverse 
ligament of the perineum, thus reaching the space between the two layers of the triangular 
ligament, where it lies above the membranous part of the urethra, and is enclosed in some 
of the fibres of the compressor urethra. Passing through the posterior layer of the tri- 
angular ligament, it enters the pelvis, and terminates, cusually by two branches, in the 
prostatico-vesical plexus. 
The dorsal vein of the clitoris in the female has a similar course to that of the deep 
dorsal vein of the penis in the male. It terminates in the inferior vesical plexus. 
THE VEINS OF THE LOWER EXTREMITY. 
The veins of the lower extremity, like those of the upper extremity, are arranged 
in two groups, the superficial and the deep, and in the lower as in the upper mb 
the deep veins are associated with the arteries as venee comites, whilst the super- 
ficial veins, which he in the subcutaneous tissues, ultimately terminate in the deep 
veins. ‘There is, therefore, a general similarity in the arrangement of the veins of 
the upper and the lower lial s, but there are differences in the details of the arrange- 
ment which are of some importance. Thus in the upper extremity there are two 
deep veins with each artery from the fingers to the root of the hmb, where a single 
trunk, the axillary vein, is formed; but in the lower extremity each main artery 
has two venve comites only as far as the middle of the mb, where a single trunk 
is formed. This vessel, the popliteal vein, is the commencement of the main venous 
stem of the lower extremity; it is continued upwards through the thigh as the 
femoral vein, and along the brim of the pelvis as the external iliac vein, which 
terminates by uniting with the internal iliac vein to form the common iliac vein. | 
Further, the superficial veins of the upper limb are more numerous than those ~ 
of the lower limb, for in the forearm there are four main superficial veins, and in | 
the leg two; in the arm two main superficial veins, and in the thigh only one. 
In the upper limb the blood which passes through the superficial veins 1s poured 
into the efferent trunk vein at the root of the limb, that is, into the axillary vein ; i 
but in the lower limb the blood from the superficies of the outer parts of the leg 
and foot passes into the commencement of the main efferent vein, the popliteal 
vein, at the middle of the limb, that is, in the region of the knee, whilst the 
blood from the superficial parts of the inner aspeet of the lower limb is poured into 
the femoral vein near the root of the hmb in the upper part of Scarpa’s triangle. 
In addition to the above-mentioned differences in the general arrangement of the 
veins of the upper and the lower extremities, it must also be noted that in the upper 
extremity all the blood of the limb, both that from the shoulder-girdle region as 
well as that from the projecting portion of the limb, is returned to the main 
efferent venous trunk ; but in the lower extremity the greater part of the blood from 
the region of the pelvic girdle, and a considerable portion from that of the thigh, is 
returned by the gluteal, obturator, sciatic, and pudic veins to the internal iliac 
vein, which in the radult is not the main efferent vein of the lower extremity. 
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