596 DISSECTION OF THE THIGH. 



The POPLITEAL VEIN (fig. 203, h) originates in the union of the vena? 

 ccmites of the anterior and posterior tibial vessels, and lias the same ex- 

 tent and connections as the artery it accompanies. At the lower border of 

 the popliteus muscle the vein is internal to the arterial trunk ; between 

 the heads of the gastrocnemius it is superficial to that vessel ; and thence 

 to the opening in the adductor magnus it lies to the outer side, and close 

 to the artery. It is joined by branches corresponding with those of the 

 artery, as well as by the short saphenous vein (fig. 203). 



The POPLITEAL NERVES (fig. 202) are the two large trunks derived 

 from the division of the great sciatic in the thigh ; they are named inter- 

 nal and external from their relative position. In the popliteal space each 

 furnishes cutaneous and articular offsets, but only the inner one supplies 

 branches to muscles. 



The INTERNAL POLiTEAL NERVE ( 2 ) is larger than the external, and 

 occupies the middle of the ham : its connections are similar to those of the 

 artery, that is to say, it is partly superficial and partly covered by the gas- 

 trocnemius. Like the vessel it extends through the back of the leg, and 

 retains the name popliteal only to the lower border of the popliteus mus- 

 cle. Its position to the vessels has been already noticed. The branches 

 arising from it here are the following : 



a. Two small articular twigs (fig. 203, 9 ) are furnished to the knee 

 joint with the vessels. One which accompanies the lower internal articu- 

 lar artery to the fore part of the articulation is the largest ; and another 

 takes the same course as the azygos artery, and enters the back of the 

 joint with it. 



b. Muscular branches arise from the nerve between the heads of the 

 gastrocnemius. One supplies both heads of the gastrocnemius and the 

 plantaris. Another descends beneath the gastrocnemius, and enters the 

 cutaneous surface of the soleus. And a third penetrates the popliteus at 

 the under aspect, after turning round the lower border. 



c. The external saphenous nerve (fig. 207, 5 ) (ram. communicans tibialis) 

 is the largest branch, and is a cutaneous offset to the leg and foot. It lies 

 on the surface of the gastrocnemius, but beneath the fascia, as far as the 

 middle of the leg, where it becomes cutaneous, and will be afterwards 

 seen. 



The EXTERNAL POPLITEAL NERVE (fig. 202, s ~) (peroneal) lies along 

 the outer boundary of the ham as far as the knee joint ; at that level it 

 leaves the space and follows the edge of the biceps muscle for two inches, 

 till it is below the head of the fibula. There it enters the fibres of the 

 peroneus longus, and divides beneath that muscle into three musculo- 

 cutaneous, anterior tibial, and recurrent articular. Its branches whilst in 

 the popliteal space are cutaneous and articular. 



a. The articular nerve, arising high in the space, runs with the upper 

 external artery to the outer side of the knee, where it sends a twig along 

 the lower articular artery : both enter the joint. 



b. The peroneal communicating branch (fig. 207, 4 ) (ram. communi- 

 cans fibularis) joins the external saphenous branch of the internal popli- 

 teal about the middle of the leg. It soon becomes cutaneous, and offsets 

 are given by it to the back of the leg. 



c. One or two cutaneous nerves are furnished by the external popliteal 

 to the integument on the outer side of the leg in the upper half. 



The articular branch of the obturator nerve (fig. 203, "') perforates the 

 adductor magnus, and is conducted by the popliteal artery to the back of 



