392 PRACTICAL ANATOMY. 



the groove to the tendons, and from tendon to tendon, in the ligamenta vaginales 

 of the digits of the lower as well as the upper extremity. By means ot these 

 vincula capillary vessels reach the synovial membrane of the tendon. 



The Internal Plantar Nerve. Begins under the internal annular ligament 

 at the bifurcation of the posterior tibial nerve. It lies between the first and second 

 layers of muscles in the sole of the foot. (Fig. 272.) It gives off: (i) Articular 

 branches to the tarsus and metatarsus and phalangeal articulations ; (2) a cuta- 

 neous branch to the skin of the heel (Fig. 272) ; (3) digital branches to the 

 inner three and one-half toes ; (4) muscular branches to the abductor hallucis, 

 flexor brevis hallucis, flexor brevis digitorum, and two lumbricals. 



The External Plantar Nerve. Begins at the bifurcation of the posterior 

 tibial ; it accompanies the external plantar artery into the sole of the foot. This 

 nerve is similar in its distribution to the ulnar nerve. It supplies a larger number 

 of muscles, still it is smaller than the internal plantar. The muscles innervated 

 by this nerve are: (i) All the interossei, seven in number, four dorsal and 

 three plantar ; (2) two lumbricals on the outer side ; (3) adductor hallucis ; 

 (4) the transversus pedis. This nerve also supplies one and one-half toes 

 the flexor accessorius and abductor minimi digiti. 



The Internal Plantar Artery (Fig. 273). This is a small artery. It 

 begins with the external plantar ; at the bifurcation of the posterior tibial artery 

 under the internal annular ligament. It accompanies the internal plantar nerve. 



The External Plantar Artery (Fig. 273). This is the larger plantar 

 artery. It crosses the sole of the foot obliquely to the head of the little toe meta- 

 tarsal, lying, of course, in common with all the other plantar structures, between 

 the first and second layers of muscles ; here it turns abruptly inward and forward 

 to the first intermetatarsal space, where it anastomoses with the communicating 

 branch of the dorsalis pedis artery, to complete the plantar arterial arch. 



The Plantar Arterial Arch. This arch is formed between the external 

 plantar artery and the dorsalis pedis. This arch lies deep -on the interossei 

 muscles. It sends off digital branches to the outer three and one-half toes. 

 At the clefts of the toes these digital branches send off perforating branches, 

 which, passing up through the interosseous spaces, communicate with the meta- 

 tarsal artery on the dorsum of the foot. 



Study the origin, insertion, and function ot muscles on your dissection, and 

 use the tabulated list of muscles that each student is expected to prepare for 

 himself for reference. 



Name the muscles of the first layer of the sole of the foot, giving their origin 

 insertion, nerve-supply and blood-supply, and action. 



The Abductor Hallucis. Origin, from the plantar fascia ; greater tuberosity o 

 os calcis ; intermuscular fascia between itself and the flexor brevis digitorum. 

 Insertion, under surface of base of first phalanx of the great toe. This muscle 

 abducts and flexes the great toe. Nerve-supply, the internal plantar nerve. 



The Abductor Minimi Digiti. Origin, plantar fascia ; lesser tuberosity of the 

 os calcis ; the intermuscular septum between itself and the flexor brevis digi- 

 torum ; the long plantar ligament. Insertion, under surface of base of first phalanx 

 of little toe. This muscle abducts the little toe from the mid-line. Nerve-supply, 

 the external plantar. 



The Flexor Brci v\ Digitornin.- Origin, the plantar fascia ; the greater tuber- 

 osity of the os calcis ; the lateral intermuscular fascia. Insertion, into the sides 

 of the middle phalanges. These tendons are perforated by the tendons of the 

 flexor longus digitorum. Nerve-supply, the internal plantar. 



Name the muscles of the second layer of the sole of ike foot, giving origin, inser- 

 tion, function, and ncn'c-snpply. 



Tlic Mnscnliis Accessorius. Origin, tin- concave inner surface of the os calcis 







