306 PRACTICAL ANATOMY. 



triangle and Hunter's canal. It becomes cutaneous, by piercing the deep fascia, 

 two inches below the knee, between the gracilis and sartorius muscles. It joins 

 company at this place with the vein of like name, and is distributed to the skin 

 of the inner side of the leg, foot, and great toe. This nerve has its extensive 

 distribution below the knee, to supply the fullest insertion of the sartorius 

 muscle and thereby verify Hilton's law. 



The Short Saphenous Nerve. This nerve has a double formation : a 

 branch from the internal popliteal, called the coiinnnnicans tibia/is, joins a branch 

 from the external popliteal, called the comrnunuans fibiilaris, to form this nerve. 

 This union may take place high or low. The nerve accompanies a vein of like 

 name, and is distributed to the skin on the posterior part of the leg and the outer 

 part of the foot and little toe. 



The Cutaneous Branch of the Musculo-cutaneous Nerve (Fig. 209). 

 This is a branch of the external popliteal nerve. The cutaneous branches are 

 distributed to the dorsum of the foot. The muscular branches of this nerve 

 supply the peronei muscles. Anastomosis takes place between these cutaneous 

 branches and also between the plantar nerves on the bottom of the foot, forming 

 the general cutaneous pedal anastomosis. 



The middle cutaneous nerve, a branch of the anterior crural, is usually found 

 as two parallel branches, one of which crosses the sartorius, the other of which 

 pierces the muscle. They end in the patellar plexus, having supplied the skin 

 on the front of the thigh. (Fig. 21 1.) 



The internal cutaneous nerve, a branch of the anterior crural, supplies the skin 

 of the inner part of the thigh ; supplies the skin over the primaiy insertion of the 

 sartorius ; assists the obturator in forming the subsartorial plexus, and ends in 

 the patellar plexus. (Fig. 211.) 



What is to be understood by tlic primary insertion of the sartorius f 



The insertion of the muscle into the upper and inner one-third of the tibia. 

 (Fig. 207.) The secondary insertion of the muscle is coextensive with the perios- 

 teum of the inner surface of the tibia ; hence to carry out Hilton's law, the long 

 saphenous branch of the anterior crural nerve has its distribution below the knee. 



How do structures became cutaneous / 



Cutaneous nerves become cutaneous by piercing the deep fascia. The hole 

 through which the nerve comes is called an opening, and takes the technical name 

 of the structure transmitted. Where several structures pass through one open- 

 ing, the largest structure lends its name to the opening. Cutaneous structures 

 piercing the deep fascia are centrifugal and centripetal. The former, as nerves 

 and arteries, have their origin below the deep fascia and their explosion in the 

 skin beyond ; the latter, as veins and lymphatics, are made up in the skin, and, 

 having collected all their tributaries, pass through the deep fascia, to become 

 themselves tributary to deep vessels or glands. 



How dissect the cutaneous nerves of the thigh f 



There are two procedures, both of which must be closely followed : (i) 

 Locate in figure 209 the opening where a given nerve comes through ; then, 

 with your forceps, plow through the fat in the long axis of the limb, always 

 downward never from side to side until you find the emergence of the nerve. 

 The location of these openings is never constant ; they may vary several inches 

 in any two cases. After having found the nerve, then trace the same out to its 

 several branches. (2) We trace out the cutaneous nerves of the thigh by locat- 

 ing and lifting up, on the finger, the main trunk of the anterior crural nerve. 

 This nerve is found under Poupart's ligament, beneath the deep fascia, in a groove, 

 between the iliacus and psoas magnus muscles. The nerve once on the finger, 

 and on the stretch, now plow downward with the forceps never with the 

 scalpel in the direction of the branches given off. In this way you can find 



