1412 



VENOUS SYSTEM. 



space. It is consequently situated between 

 the artery and the posterior tibial nerve. 



The valves in this vein are four or five in 

 number. Its coats are stated by Cruveilhier 

 and others to be of more than ordinary thick- 

 ness. 



The femoral vein is the continuation of the 

 poplitaeal, which latter vessel, having passed 

 through the tendinous opening in the adduc- 

 tor muscles, enters the thigh, and becomes 

 femoral. In the lower third of the thigh the 

 femoral vein and artery (enclosed in a com- 

 mon sheath) are contained in " Hunter's 

 canal," the vein lying, as in the ham, posterior 

 and external to the artery. In the centre of 

 the thigh the vein is placed directly behind 

 the artery ; but throughout its upper third the 

 two vessels lie side by side, and in close con- 

 nection, the vein being the more internal. 

 A thin, fibrous septem derived from the sheath 

 which surrounds them passes backwards, and 

 separates these vessels at this part of their 

 course. The point of the aneurism needle is 

 apt to be entangled by this partition, in con- 

 veying a ligature round the femoral artery, if 

 care be not taken to keep the instrument on 

 its outer or arterial side, whilst at the same 

 time the sheath is kept tense. At the highest 

 point of its course, just where it is about to 

 pass beneath Poupart's ligament, the femoral 

 vein constitutes the external boundary of 

 the crural ring, and would therefore neces- 

 sarily bear the same relation to the neck of 

 any hernial tumour which may have descended 

 through this aperture. In its course through 

 the thigh, the femoral vein is joined by nu- 

 merous muscular branches, also by the profunda 

 vein, about an inch and a half below the 

 crural arch, and, lastly, by the internal saphena 

 vein. 



Its valves are from three to five in number. 



Beneath Poupart's ligament the femoral 

 becomes continuous with the external iliac 

 vein. 



The external iliac vein, whilst it accom- 

 panies the external iliac artery, and holds the 

 same relation to surrounding parts as that 

 vessel, is nevertheless differently related to 

 its artery on the right and left side. As these 

 vessels lie on the horizontal ramus of the 

 pubis, their relative positions at both sides is 

 the same, the vein being placed internal to 

 the artery. On the left side this relation does 

 not alter, and the vein lies on the inner side 

 of the artery throughout its whole course ; 

 on the right side, however, the vein, in its 

 ascent, passes first behind the artery, and 

 then appears slightly to its outer side. 



The internal circumflex ilii and the two 

 deep epigastric veins join the external iliac 

 vein at the commencement of its course im- 

 mediately above Poupart's ligament. The 

 former holds a remarkable relation to the ex- 

 ternal iliac artery, for it crosses that vessel at 

 right angles to its anterior surface, and thus 

 separates the artery from the fascia transver- 

 sails. 



The internal iliac vein is formed in the 

 cavity of the pelvis by the union of the veins 



which correspond to the numerous divisions of 

 the internal iliac artery, viz. by the glutatal, 

 sciatic, internal pudic, and obturator veins, all 

 of which arise external to the pelvis ; and by 

 numerous branches from the viscera contained 

 within the pelvis, and which are remarkable 

 for their plexiform arrangement. Of these, the 

 vesical veins form a plexus which surrounds 

 the neck of the bladder, and the prostate 

 gland (yesico-prostatic plexus^, receives the 

 blood from the dorsal veins of the penis, and 

 communicates freely with the inferior hcsmor- 

 rhoidal veins. In the female a similar plexus 

 receives veins from the clitoris and the labia, 

 and in addition there are two others, still 

 more remarkable for their development, the 

 vaginal plexus, which surrounds the vagina 

 near its commencement, and communicates 

 with the vesical plexus in front, and with the 

 haemorrhoidal veins behind, and the uterine 

 plexus, the veins of which are scarcely jip- 

 parent except during gestation, and which 

 communicate with the ovarian veins. 



In both sexes the lower extremity of the 

 rectum is surrounded by the ramifications of 

 the hcemorrhoidal plexus, the blood of which is 

 returned to the internal iliac vein by the 

 middle and inferior haemorrhoidal veins. This 

 plexus likewise communicates freely with the 

 superior hcBmorrhoidal veins, which unite with 

 the inferior meseraic veins, and so constitute 

 a part of the portal system. 



In all these vessels valves exist in great 

 numbers, although none occur in the great 

 trunks in which they terminate. 



The internal iliac vein on each side is in- 

 ternal to its corresponding artery. 



The common iliac veins are formed by the 

 union of the external and internal iliac veins. 

 The junction takes place opposite the sacro- 

 iliac symphisis. These veins exhibit on each 

 side some interesting anatomical peculiarities. 



The right common iliac vein, nearly vertical in 

 its direction, is placed posterior and external, 

 to its corresponding artery. 



The left common iliac vein, larger than the 

 preceding, and nearly transverse in its direction, 

 lies internal, and inferior, to its corresponding 

 artery, and crosses behind the common iliac 

 artery of the right side. 



The common iliac veins usually unite upon 

 the intervertebral substance between the fourth 

 and fifth lumbar vertebrae, to form the vena 

 cava inferior. The junction occurs to the 

 right of the mesial line, and inferior to, as well 

 as to the right of, the angle of bifurcation of 

 the aorta.* 



The collateral branches of the common iliac 

 veins are the following : 



(a) The i/io-lumbar vein. This vein arises in 

 the iliac fossa, by radiating branches, which 



* The junction of the venae innominatae to form 

 the superior vena cava, as well as that of the com- 

 mon iliac veins to form the inferior vena cava, oc- 

 curs on the right of the mesial line of the body. 

 In the former instance, the uniting veins are found 

 on a plane anterior to the arterial trunks which 

 they accompany ; whilst in the latter they lie be- 

 hind them. 



