IIO THE HUMAN BODY. 



spending in name to the arteries of the upper limb; it is also 

 the common trunk of the superficial veins of the hand, fore- 

 arm, and arm, the principal of which are the cephalic and 

 basilic. This last vein crosses the radial artery in the bend 

 of the elbow, and is separated from it by a tendinous expan- 

 sion of the biceps muscle. The cephalic and basilic veins are 

 those most commonly opened in blood-letting; this operation 

 is rendered delicate by the situation of the basilic, which ex- 

 poses the artery to the danger of being wounded. 



The azygos vein (azygos, without a fellow) forms the com- 

 munication between the superior and inferior vena cava. It 

 rises vertically in the posterior mediastinum and to the 

 right of the spine, and about the level of the seventh rib it 

 receives the lesser vena azygos, which comes from the abdomen. 



The inferior vena cava opens into the right auricle under 

 the superior vena cava. It is the common trunk of all the 

 veins coming from the parts below the diaphragm, and is 

 formed by the union of the two iliac trunks, companions of 

 the iliac arteries; it runs up vertically to the right of the 

 spine as companion vein to the aorta, and receives the veins 

 of the abdomen. Its primitive branches, the iliac trunks, are 

 formed by the union of the veins of the pelvic cavity and of 

 the lower extremities, companions of the arteries of the same 

 name. Among the superficial series of veins, which are also 

 tributaries to the main iliacs, are the external and internal 

 saphenons veins, which run from the foot to the top of the 

 thigh. These two veins are plainly visible on the front of 

 the ankle and on the calf. 



Portal system. An arrangement of veins peculiar to the 

 abdomen, and especially to the liver, is designated by this 

 term. The portal vein is formed by the union of the veins 

 of the mesentery, spleen, stomach, and intestine; it trans- 

 mits the blood from these organs to the liver, from whence 

 it is poured into the inferior vena cava. 



Lymphatic vessels and ganglia. This is the name given 

 to a special circulatory apparatus composed of very delicate 

 vessels with transparent walls and Q{ ganglia or glands, which 

 appear to be formed by these vessels, some of which ter- 

 minate in and others spring from them. 



