VEINS. 255 



. PeroneaL Arises an inch below origin of posterior 

 tibial artery. It is almost as large as the posterior tibial, 

 and runs down between the superficial and deep group 

 of muscles to the fibular side of the leg. Its branches 

 are the muscular and the nutrient to the fibula. The 

 posterior tibial becomes the plantar artery, which di- 

 vides into the internal plantar and the external. The 

 internal is small, and supplies the inner side of the foot. 

 The external plantar is large, runs outward to the base 

 of the fifth metatarsal, then curves deeply inward, form- 

 ing the plantar arch, which is completed by a communi- 

 cating branch from the dorsalis pedis. The external 

 plantar sends off () the Perforating, which anastomoses 

 with the dorsalis pedis ; (6) the Digital, four or five 

 vessels to the toes. Each branch runs forward to the 

 web of the toe, then divides into two branches, which 

 are distributed to the adjoining sides of the toes. 



THE PULMONARY ARTERY. 



The pulmonary artery, about two inches long, arises 

 from the right ventricle, and carries venous blood to the 

 lungs. It divides into the right and left pulmonary, which 

 pass to the right and left lungs respectively, then divide 

 and subdivide, and finally form plexuses or anastomoses, 

 reticular in character, around the air-cells ; they are so 

 arranged that the diameter of the mesh is less than the 

 diameter of the capillary. The pulmonary capillaries are 

 exquisitely delicate, and consist of a single layer of 

 endothelial cells jointed together by an albuminoid 

 cement-substance. 



VEINS. 



The systemic veins are vessels which carry the venous 

 blood to the heart. They begin in the capillaries, grad- 

 ually increase in size, and terminate in the ascending and 



