306 INFERIOR EXTREMITY 



Dissection, A satisfactory display of the interosseous muscles cannot be 

 obtained unless the transverse ligament be divided between the heads of 

 the metatarsal bones. The toes can now be separated more freely from 

 each other, and the interosseous muscles traced to their insertions. It is 

 well also to reflect, at this stage, the flexor brevis digiti quinti. 



Interosseous Muscles. The plantar interosseous muscles 

 are three in number, and are so placed that they adduct the 

 three lateral toes towards a line drawn through the second 

 toe. They arise from the plantar aspects of the three lateral 

 metatarsal bones, and each is inserted upon the medial side of 

 the first phalanx of the corresponding toe. The dorsal inter- 

 osseous muscles are four in number. They occupy the four inter- 

 metatarsal spaces, and consequently they must be dissected 

 both upon the plantar and dorsal aspects of the foot. They 

 are arranged so as to abduct the second, third, and fourth 

 toes from a line drawn through the second toe. They are 

 inserted, therefore, as follows : the first upon the medial side of 

 the second toe ; the second upon the lateral side of the same 

 toe ; the third upon the lateral side of the third toe ; and the 

 fourth upon the lateral side of the fourth toe. The slender 

 tendons of the interosseous muscles are only very slightly 

 attached to the bases of the proximal phalanges. They are 

 for the most part inserted into the expansions of the extensor 

 tendons on the dorsal aspect of the toes. 



Tendon of the Tibialis Posterior. Before leaving the sole 

 of the foot the dissector must determine the precise insertions 

 of the tendons of the tibialis posterior and of the peronaeus 

 longus. The tendon of the tibialis posterior is not merely 

 inserted into the tubercle of the navicular bone. Fibrous 

 slips are seen to spread out from it, and these may be traced 

 to every bone of the tarsus with the exception of the talus, 

 and also to the bases of the second, third, and fourth meta- 

 tarsal bones. As it lies under and gives support to the head 

 of the talus, the tendon of the tibialis posterior has developed 

 within it a sesamoid nodule of fibre-cartilage, or perhaps a 

 sesamoid bone. 



Tendon of the Peronaeus Longus. The tendon of the 

 peronaeus longus turns round the lateral margin of the foot, 

 and runs medially, across the sole, in the groove on the plantar 

 surface of the cuboid bone, to reach the base of the first 

 metatarsal bone. As it traverses the sole it is enclosed in a 

 fibrous sheath. This sheath is mainly formed by fibres 

 derived from the long plantar ligament. Open the sheath 



