THE LOWER LIMB 547 



flexor sheath anteriorly ; and (3) at each side of the flexor tendons 

 it sends a deep process upwards, which joins the transverse meta- 

 tarsal (deep transverse) ligament connecting the heads of the 

 metatarsal bones, and is also attached to the corresponding 

 lateral metatarso-phalangeal ligament. There is thus formed a 

 tunnel for the passage of the flexor tendons. The lumbricales 

 muscles and the digital vessels and nerves make their appearance 

 between the diverging digital processes. The central division 

 contributes to the maintenance of the longitudinal arch of the 

 foot by its tendency to approximate the toes to the heel. When it 

 becomes contracted it gives rise to an exaggeration of the longi- 

 tudinal arch, a condition known as pes cavus. Morphologically 

 it represents the divorced plantar portion of the tendon of the 

 plantaris. 



The external division is weaker than the central. It is attached 

 posteriorly to the outer tubercle on the plantar aspect of the 

 tuber calcis, whence it passes forwards over the abductor minimi 

 digiti muscle. Internally it is continuous with the central division 

 along the line of attachment of the external intermuscular septum ; 

 externally it is continuous round the outer border of the foot 

 with the deep fascia of the dorsum ; and anteriorly, having become 

 very thin, it is attached to the proximal end of the first phalanx of 

 the little toe on its outer aspect. This division forms a specially 

 strong band between the outer tubercle of the os calcis and the 

 tuberosity on the outer side of the base of the fifth metatarsal 

 bone, which is the remains of the abductor ossis metatarsi quinti, or 

 Wood's muscle. ■ 



The internal division is the weakest of the three. It is 

 attached posteriorly to the internal aspect of the inner tubercle 

 on the plantar surface of the tuber calcis, and to the lower border 

 of the internal annular ligament, whence it passes forwards over 

 the abductor hallucis muscle. Externally it is continuous with 

 the central division along the hne of attachment of the internal 

 intermuscular septum ; internally it is continuous round the inner 

 border of the foot with the deep fascia of the dorsum ; and 

 anteriorly, where it becomes very thin, it is attached to the 

 proximal end of the first phalanx of the great toe on its inner 

 aspect. 



The intermuscular septa are two in number, external and internal, 



and they extend upwards into the sole at either side of the central 



division along the course of the longitudinal grooves. They are 



situated on either side of the flexor brevis digitorum, the internal 



septum lying between that muscle and the abductor hallucis, 



j and the external septum intervening between it and the abductor 



minimi digiti. Each septum giv^es partial origin to the muscles 



between which it hes. The plantar fascia and the two inter- 



I muscular septa form three muscular compartments — inner, middle, 



' and outer. 



Cutaneous Nerves. — The cutaneous nerves are as follows : 



