616 DISSECTION OF THE FOOT. 



little toes, and is connected with the sheath of the others as it passes over. 

 Beneath it the digital nerves and vessels issue. 



The sheaths of the flexor tendons (tig. 211, G ) are similar to those of 

 the fingers, though not so distinct, and serve to confine the tendons against 

 the grooved bones. The sheath is weak opposite the articulations between 

 the phalanges, but is strong opposite the centre of both the metatarsal 

 and the next phalanx. Each is lubricated by -a synovia! membrane, and 

 contains the tendons of the long and short flexor muscles. 



Dissection (fig. 210). In the sole of the foot the muscles are numer- 

 ous, and have been arranged in four layers. To -prepare the first layer 

 all the fascia must be taken away ; but this dissection must be made with 

 some care, lest the digital nerves and vessels, which become superficial to 

 the central muscle towards the toes, should be injured. 



The tendons of the short flexor muscle are to be followed to the toes, 

 and one or more of the sheaths in which they are contained should be 

 opened. 



FIRST LAYER OF MUSCLES. In this layer are three muscles, viz., the 

 flexor brevis digitorum, the abductor pollicis, and abductor minimi digiti. 

 The short flexor of the toes lies in the centre of the foot ; and each of 

 the others is in -a line with the toe on which it acts. 



The ABDUCTOR POLLICIS (fig. 210, A ), the most internal muscle of the 

 superficial layer, takes origin from the inner part of the larger tubercle 

 on the under surface of the os calcis ; from the plantar fascia ; and J'rom 

 the lower border of the internal annular ligament, and the inner side of 

 the foot as far as the scaphoid bone. In front the muscle ends in a ten- 

 don, which is joined by fibres of the short flexor, and is inserted into the 

 inner side of the base of the metatarsal phalanx of the great toe. 



The cutaneous surface of the muscle is in contact with the plantar 

 fascia ; and the other touches the tendons of the tibial muscles, the plantar 

 vessels and nerves, and the tendons of the long flexors of the toes with the 

 accessorius muscle. 



Action. This abductor acts chiefly as a flexor of the metatarso-phalan- 

 geal joint of the great toe, but it will abduct slightly that toe from the 

 others. 



The FLEXOR BREVIS DIGITORUM (fig. 210, B ) (flexor perforatus) arises 

 posteriorly by a pointed process from the inner part of the larger tubercle of 

 the os calcis, and from the plantar fascia and the septa. About the centre 

 of the foot the muscle ends in four small tendons, which are directed for- 

 wards over the tendons of the long flexor, and entering the sheaths of the 

 four smaller toes, are inserted into the middle phalanges. In the sheath 

 of the toe the tendon of this muscle lies at first (in this position of the 

 foot), on the long flexor; opposite the centre of the metatarsal phalanx it 

 is slit for the passage of the other, and is attached by two processes to the 

 sides of the middle phalanx. 



The short flexor of the toes is contained in a sheath of the plantar 

 fascia, and occupies the middle of the foot. It conceals the tendon of the 

 long flexor of the toes, the accessory muscle, and the external plantar 

 vessels and nerve. 



Action. It bends the nearest phalangeal joint of the four smaller toes, 

 like the flexor sublimis in the upper limb, and approximates the toes at 

 the same time. 



The ABDUCTOR MINIMI DIGITI (fig. 210, c ) has a wide origin behind 

 from the outer tubercle of the os calcis, from the fore part of the inner 



