108 THE HUMAN BODY. 



will mention only the coeliac trunk, which divides into three 

 branches, destined to the liver, the stomach, and the spleen; 

 the superior and inferior mesenteric, which go to the mesentery 

 and intestines; and the renal or emulgent arteries. 



Iliac arteries. The common iliac arteries, formed by the 

 bifurcation of the aorta, run obliquely downward to the 

 right and left. After attaining a length of about two and a 

 half inches, each one divides into the internal iliac, which 

 ramifies on the inside and on the outside of the pelvic 

 cavity, and the external iliac, which at the point where it 

 leaves the pelvis gives off the epigastric artery. This artery 

 runs upward behind the anterior wall of the abdomen, and 

 unites by anastomosis with the lower extremity of the internal 

 mammary artery. On leaving the pelvis the external iliac 

 takes the name of \hzfemoral artery, gives off large branches 

 to the muscles of the thigh, and on reaching the lower third 

 of this region, becomes the popliteal artery, or artery of the 

 ham. This last gives off the anterior tibial, and then divides 

 into the posterior tibial and the peroneal artery. The anterior 

 tibial at the point of the articulation of the foot with the leg 

 takes the name of dorsal artery of the foot, and ramifies over 

 the upper surface of the foot; while the peroneal and posterior 

 tibial, after having, like the anterior tibial, distributed branches 

 to the leg, terminate in the plantar, region, or sole of the foot 



Veins. The veins carry the blood from the extremities to 

 the heart. They are divided like the arteries into two classes, 

 according as, filled with red blood, they run from the capil- 

 laries of the lungs to the trunks of the pulmonary veins 

 which is the lesser circulation; or as they carry the black 

 blood to the venae cavae which is the general circulation. 

 The veins of the liver and their principal trunk, the portal 

 vein, have sometimes been considered as also a separate 

 system; and this distinction has also been extended to those 

 of the kidneys and other organs. 



The walls of the veins are much thinner than those of the 

 arteries, and are formed of four tunics, of which the fourth 

 or internal one is like that of the arteries; the others are 

 formed of elastic or cellular fibres, longitudinal in the third, 

 circular in the second, in such a manner as to present the 



