THE VEINS. 241 



d. The Aiieria inleros-^ea (Fig. 158 i) arises from the dorsal 

 artery of the foot at the tarsus, and perforates the membrane 

 between the astragahis and calcaneum to reach the sole of the foot. 

 It forms a rich subcutaneous plexus on the calcar, and anasto- 

 moses with the Rami perforantes (Fig-. i5^j]f), which pass above 

 the upper borders of the Musculi infer ossei to reach the plantar 

 surface, where they g-ive off small Bami inferossei volares to 

 anastomose with the A A. inierosseae dorsales. 



III. THE VEINS. 



(The arrangement of this section has been modified.) 



The blood, distributed to the body by means of the arteries, is 

 returned to the heart by the veins, which conduct the blood di- 

 rectly or indirectly to the auricles. The pulmonary vein opens 

 directly into the left ventricle, the three Venae cavae open into the 



Sinus venosus. 



A. Vein opening into the left auricle. 



The pulmonary vein [Vena pulmonalls communis), (Fig. 159 

 rp). The blood returning from each lung is gathered into a 

 vessel lying along the inner side of the root of the lung. That of 

 the right side is somewhat longer than the left ; the two vessels 

 [fenae pulmonales dextra et sinistra) run above the corresponding- 

 anterior caval veins to form a common trunk, the pulmonary vein, 

 which opens into the left auricle (see p. 215). 



B. Veins opening into the Siniis venosus. 



The veins opening into the Sinus venosus are the three caval 

 veins ; of these the two anterior open into the anterior angles of 

 the Sitms venosus, the posterior into the posterior angle. 



1. The Anterior Caval Veins [Vena cava superior), (Figs. 133 V, 

 159 C a) are a pair of large veins opening into the Sinus venosus 

 and returning to it blood from the fore-limbs and sides of the head. 

 Each vein is formed by the union of a small vein, the external jvigu- 

 lar, with two large veins, the innominate and the subclavian veins. 



a. The external jugular vein [Vena jugularis externa), (Fig. 

 i^gje) is formed, at the outer border of the hyoid bone, by the 

 union of two veins : — 



(1) The lingual vein [Vena linffualis) (Fig. 16 1 1). This originates 

 at the tip of the tongue and passes in a very tortuous course along 

 the ventral surface of the hyoid; it receives numerous branches 

 from the tongue and hyoid muscles. 



E 



