PORIFERA. 



have been recorded of a high division of the 

 femoral artery (see FEMORAL ARTERY), and 

 where two popliteal arteries existed ; but the 

 artery generally appears particularly free from 

 any variety. 



Branches of the popliteal artery. These are 

 very numerous, and of considerable importance 

 in maintaining a collateral circulation when the 

 femoral artery has been obliterated by operation 

 or disease ; they are not always constant, either 

 in number or s'ize. The popliteal artery first 

 sends some irregular branches to the hamstring 

 muscles, the rami musculares superiores ; then 

 five articular arteries, two of which usually 

 arise a little above the joint, and are called ex- 

 ternal and internal superior articular, and two 

 below, the external and internal inferior arti- 

 cular ; the last is an azygos branch. After giving 

 off these articular arteries, the popliteal sends 

 several large branches to the gastrocnemii 

 muscles, the rami musculares inferiores. 



The superior muscular branches are two or 

 three in number, which are distributed on either 

 side to the hamstring muscles and anastomose 

 with the perforating arteries of the profunda. 

 The superior external articular artery is of some 

 size, and arises from the outer side of the popli- 

 teal at a variable distance above the outer con- 

 dyle of the femur; it descends to wind round 

 the bone under the biceps muscle, which latter 

 it supplies and divides into superficial and deep 

 branches ; the former are distributed to the vas- 

 tus externus muscle, and, by passing through 

 its substance, terminate on the patella ; the lat- 

 ter supply the synovial lining of the articulation, 

 and the lower extremity of the femur itself. 

 These branches anastomose with those of the 

 inferior external articular artery, and with the 

 long branches of the external circumflex from 

 the profunda, which descend in the substance 

 of the vastus externus towards the knee. 



The superior internal articular artery arises 

 from the inner side of the popliteal above the 

 inner condyle.and also winds round the femur, 

 passing beneath the tendon of the adductor 

 magnus muscle; like the external articular, it 

 divides into superficial and deep branches, the 

 former penetrating the vastus internus to ramify 

 on the patella, and anastomoses with the ex- 

 ternal articular and the anastomotica magna 

 from the femoral; the deeper branch is distri- 

 buted to the synovial capsule and femur. 



The azygos branch is derived from the ante- 

 rior aspect of the popliteal while it is in relation 

 with the posterior ligament of the joint ; it di- 

 vides into branches which pass through the liga- 

 ment, and supply the synovial membrane and 

 crucial ligaments of the joint. The inferior ex- 

 ternal articular is given off from the outer side 

 of the popliteal a little below the articulation, 

 and winds round the outer surface of the ex- 

 ternal semilunar cartilage, passing beneath the 

 plantaris and outer head of the gastrocnemius 

 muscles ; it then courses forward above the 

 head of the fibula, and beneath the external 

 lateral ligament to divide into branches, which 

 anastomose with the anterior tibial recurrent 

 and the other articular arteries. The inferior 

 internal articular artery is generally rather a 



large branch, and descends to the internal lateral 

 ligament, beneath which it passes to gain the 

 front of the tibia; it divides into numerous 

 branches which are distributed to the structures 

 about the inner side of thejoint, and which anas- 

 tomose also with the other articular branches. 



These articular branches of the popliteal are 

 seen, when well injected, to form a beautiful 

 network of vessels around the knee-joint; by 

 anastomosing with the external circumflex and 

 perforating branches of the profunda, with the 

 anastomica of the femoral and the recurrent 

 tibial artery, and also with each other, a very 

 sufficient collateral circulation is usually main- 

 tained in cases where the femoral artery has 

 been obliterated.* 



The inferior muscular branches are derived 

 from the popliteal artery while passing between 

 the heads of the gastrocnemius ; they are four 

 or five in number, and often of considerable 

 size; accompanied by branches from the tibial 

 nerve, they descend in the substance of the 

 gastrocnemii muscles, and maybe traced some- 

 times to the tendo Achillis ; generally, a small 

 branch from one of them descends with the 

 communicans tibialis nerve. These vessels are 

 sufficiently large as occasionally to require a 

 ligature after amputation of the leg. 



The course of the popliteal vein has been 

 already noticed in connection with the artery; 

 it is remarkable for the thickness of its fibrous 

 coat, and is formed by the junction of the ante- 

 rior tibial veins with a trunk called the tibio- 

 peroneal : this latter vessel is produced by the 

 confluence of the posterior tibial and peroneal 

 veins. The popliteal vein receives the veins 

 which accompany the branches of the popliteal 

 artery, and also, about the centre of this re- 

 gion, the vena saphena minor. 



Operative relations of the popliteal artery. 

 Operations upon the artery in this region are 

 now never undertaken, unless, perhaps, in cases 

 of injury with an external wound, the size and 

 direction of which will vary the surgical treat- 

 ment to be adopted ; a ligature may be passed 

 round the artery in the upper part of its course 

 as it emerges from beneath the semimembra- 

 nosus muscle, the outer edge of which will act 

 as a guide to the first incision. After dividing 

 the fascia, the finger, sunk into the space and 

 carried upwards upon the outer surface of the 

 semi-membranosus, will reach the artery ; the 

 vein lies behind it, and a little to the outer side, 

 and will therefore be reached first ; the needle 

 must be insinuated between the artery and vein, 

 and carried round the former from without in- 

 wards. This operation is mentioned merely as 

 being practicable ; in the rest of its course the 

 relations of the artery are such as to prohibit 

 any surgical operation upon it. 



(William Trew.) 



PORIFERA (TTO'POS 4>ep<" canal-bearing"). A 

 word applied by Professor Grant to designate 



* I have witnessed one instance where mortifica- 

 tion of the leg ensued after the application of a 

 ligature to the femoral artery for the cure of popli- 

 teal aneurism; amputation was performed above 

 the knee. 



