BRANCHES OF THE INFERIOR YENA CAVA. 495 



oblique in their direction, those from the middle of the liver and the 

 lobule of Spigelius have an intermediate position and course. The 

 hepatic veius have no valves ; but, owing to their oblique entrance 

 into the vena cava, a semi-lunar fold is seen at the lower border of the 

 orifice of each vein. 



Varieties. — The lower vena cava presents some occasional deviations from its 

 ordinary condition, which may be briefly noticed. 



In the lower part of its course it is sometimes placed to the left side of the 

 aorta, and. after receiving the left renal vein, resumes its ordinary position by 

 crossing over the great artery. Less frequently, the vena cava is placed alto- 

 gether on the left side, and is continued upwards to the heart, without any 

 change in its direction ; this occui's in cases of transposition of the thoracic 

 and abdominal viscera and of the great vessels. 



In a more numerous class of cases, the left common iliac vein, instead of 

 joining the right in its usual position, is connected with it only by a small 

 branch, and then ascends on the left side of the aorta. After receiving the left 

 renal vein, it crosses over the aorta, and terminates by uniting with the common 

 iliac vein of the right side. In these cases, the vena cava inferior can be said 

 to exist only at the upper part of the abdomen, and below this point there is a 

 vein on each side of the aorta. 



Lastly, the lower vena cava, instead of ending in the right auricle of the heart, 

 has been seen to join the right azygos vein, which is then -s-ery large so that the 

 )]lood from the lower, as well as from the upper part of the body, is returned to 

 the heart through the upper vena cava. In this case, the hepatic veins do not 

 join the lower cava, but pass directly into the right auricle, at the usual place of 

 termination of the great vein. (Specimen in Glasgow University Museum.) 



The left renal vein has been seen to cross behind the aorta. 



In a remarkable case, observed by Rothe, one of the hepatic veins ended, not 

 in the lower cava, nor in the right auricle, but in the right ventricle of the heart, 

 its orifice being guarded by valves. (Act. Acad. Joseph. Med. Chir. Yindobonensis, 

 t. i. p. 233, tab, o. Yindobons, 1788.) 



VEIN'S OP THE LOWER LIMB AI^D PELVIS. 



The veins of the lower limb are divisible into two sets, those of the 

 one being deeply seated, those of the other running in the superficial 

 fascia. All the veins of the lower limb, as high as the femoral venous 

 trunk, are provided with valves, and these are more numerous than in 

 the veins of the upper hmb. The deep veins have more valves than 

 the subcutaneous set. 



SUPERFICIAL VEINS OP THE LOWER LIMB. 



Immediately beneath the integument, on the dorsum of the foot, 

 there exists a network of veins forming an arch, from which issue two 

 principal trunks, which are named the internal or long and the external 

 or short saphenous veins. 



The internal or long saphenous vein extends from the ankle to 

 within an inch and a half of Poupart's ligament. Taking rise fi-om 

 the plexus of veins on the dorsum of the foot, it passes upwards in 

 front of the inner ankle, and along the inner border of the tibia, 

 accompanied by the internal saphenous nerve. It inclines a little 

 backwards as it passes the inner condyle of the femur, and ascending 

 along the inner and fore part of the thigh, it terminates in the femoral 

 vein, at the sajfJienous opcnii^g in the fascia lata, through which it 

 passes. 



In the leg it communicates with the deep veins accompanying the 



