POPLITEAL ARTERY AND BRANCHES. 595 



view ; the inner artery is below the head of the tibia, and the outer 

 higher up between the tibia and fibula, each with a vein, and the first has 

 a companion nerve. 



Beyond the ham. Whilst the artery is beneath the gastrocnemius (fig;. 

 208) it sinks deeply into the limb; here it is crossed by a small muscle 

 the plantaris c, and the ending is concealed by the soleus B. It rests on 

 the popliteus muscle. 



Both the companion vein and the internal popliteal nerve change their 

 position to the artery, and gradually cross over it, so as to lie on its inner 

 side at the lower border of the popliteus. 



Sometimes the artery is divided as high as the back of the knee joint ; 

 and then the anterior tibial artery may lie beneath the popliteus muscle. 



Branches' (fig. 203) are furnished by the artery to the surrounding mus- 

 cles, and to the articulation ; those that belong to the joint are five in 

 number, and are called articular, viz., two superior, inner and outer; two 

 inferior, also inner and outer ; and a central or azygos branch. 



a. The muscular branches are upper and lower. The upper set, three 

 or four in number, arise above the knee, and end in the semi-membranosus 

 and biceps muscles, communicating with the perforating and muscular 

 branches of the profunda. The lower set (sural) are furnished to the 

 muscles of the calf, viz., gastrocnemius, soleus, and plantaris. 



b. A superficial or cutaneous branch arises near the knee joint, and ac- 

 companies the external saphenous nerve over the muscles of the leg to end 

 in the teguments (fig. 203). 



c. The superior articular arteries arise from the popliteal trunk, one 

 from the inner and one from the outer side, above the condyles of the 

 femur ; they are directed almost transversely beneath the hamstring mus- 

 cles, and turn around the bone to the front of the joint. 



The external one (&) perforates the intermuscular septum, and divides 

 in the substance cf the vastus internus. Some of the branches end in that 

 muscle, and anastomose with the external circumflex (of the profunda) : 

 others descend to the joint ; and one offset forms an arch across the fore 

 part of the bone with the anastomotic artery. 



The internal artery (/), oftentimes very small, winds beneath the ten- 

 don of the adductor magnus, and terminates in the vastus internus ; it 

 supplies this and the knee joint, and communicates with the anastomotic 

 artery. 



d. The inferior articular branches (fig. 208) lie beneath the gastro- 

 cnemius, but are not on the same level on opposite sides of the limb ; for 

 the inner one descends below the head of the tibia, whilst the outer one 

 is placed above the fibula. Each lies beneath the lateral ligament of its 

 own side. 



The external branch (c) supplies she outer side of the knee joint, anas- 

 tomosing with the other vessels on the articulation, and with the recurrent 

 branch of the anterior tibial artery : it sends an offset beneath the liga- 

 ment of the patella to join a twig from the lower internal branch. 



The internal artery (6) ascends at the anterior border of the internal 

 lateral ligament, and after taking its share in the free anastomoses over 

 the joint, ends in offsets for the articulation and the head of the tibia. 



e. The azygos branch enters the back of the joint through the posterior 

 ligament, and is distributed to the ligamentous structures, the fat, and the 

 synovial membrane of the interior. 



