544 ^ MANUAL OF ANATOMY 



between the external malleolus and the tuberosity on the outer side 

 of the proximal end of the fifth metatarsal bone. The astragalo- 

 navicular and calcaneo-cuboid joints lie in the same transverse 

 plane, and are the joints at which disarticulation is performed in 

 Chopart's operation. The guide to the joint between the internal 

 cuneiform and first metatarsal bones is a point i^ inches in front of 

 the navicular tuberosity. This is to be remembered in connection 

 with the tarso -metatarsal operations of Lisfranc and Hey. The 

 joint between the cuboid and fifth metatarsal bones is situated 

 immediately behind the tuberosity on the outer side of the proximal 

 end of the fifth metatarsal bone. 



The course of the external plantar artery is complicated by the 

 fact that it first crosses the sole of the foot from within outwards, 

 and afterwards from without inwards. The former course is 

 indicated by a line drawn from a point midway between the inner 

 part of the point of the heel and the tip of the internal malleolus 

 to a point about i inch internal to the tuberosity on the outer side 

 of the base of the fifth metatarsal bone. A line drawn from the 

 latter point to the proximal part of the first interosseous space 

 indicates the position of the artery as it recrosses the foot. To 

 indicate the course of the internal plantar artery start from the 

 same point as for the commencement of the external plantar vessel, 

 and draw a line to the centre of the metatarso-phalangeal joint of 

 the great toe. 



The skin of the sole is characterized by great thickness over 

 the bony prominences of the heel and balls of the toes, in which 

 situations bursae are frequently developed. The superficial fascia 

 is coarse and granular. It forms a thick pad composed of lobules 

 of fat, which lie between, and are supported by, processes of fibrous 

 tissue passing between the skin and the plantar fascia. 

 Plantar Bursae. — These bursae are as follows: 



Calcaneal. Fifth metatarsal. 



First metatarsal. Navicular. 



Peroneal. 



♦ The calcaneal bursa is placed over the plantar aspect of the tuber 

 calcis, which has two tubercles — inner and outer. This bursa is 

 but little developed, unless in those persons who have to stand for 

 long periods of time. 



The first metatarsal bursa is situated over the plantar aspect of 

 the head of the first metatarsal bone, which supports the two 

 phalanges of the great toe or hallux. The head of this bone is of 

 large size, and its plantar surface is rendered prominent by two 

 large sesamoid bones. 



Another first metatarsal bursa is sometimes formed over the 

 internal or medial aspect of the metatarso-phalangeal joint of the 

 great toe. This occurs in cases of hallux valgus, which is an external 

 displacement or subluxation of the great toe or hallux at the meta 

 tarso-phalangeal joint. The hallux may be displaced outwards to 



