392 THE INFERIOR EXTREMITY 



where it divides into four tendons for the lateral four toes. 

 Where the tendons cross, the tendon of the flexor hallucis 

 longus gives a slip to the deep surface of the tendon of the 

 flexor digitorum longus. 



Sir William Turner called attention to the fact that the slip, which 

 passes from the tendon of the flexor hallucis longus to the tendon of the 

 flexor longus digitorum, varies greatly in magnitude and in the manner in 

 which it is connected with the flexor tendons of the toes. In the majority 

 of cases it goes to the tendons of the second and third toes or to the tendons 

 of the second, third, and fourth toes ; in some cases, however, only to 

 the tendon of the second toe. Very rarely does it divide so as to bring 

 all the tendons of the flexor digitorum longus into connection with the 

 tendon of the flexor hallucis longus. 



The musculus quadratus plantce, which is inserted into the 

 tendon of the long flexor of the toes, and also the four 

 lumbrical muscles, which arise from the flexor tendons, can 

 now be distinguished. Note the position of the long 

 plantar ligament between the two heads of origin of the 

 quadratus plantse. 



Dissection. Before the flexor tendons are traced forwards 

 to the toes, the fibrous flexor sheaths of the toes must be dis- 

 played and examined. The skin on the plantar aspects of the 

 toes has already been reflected and the digital vessels and nerves 

 have been cleaned. Now remove the remains of the superficial 

 fascia and expose the flexor sheaths. 



Each sheath consists of two strong portions, called the digital 

 vaginal ligaments, which lie opposite the bodies of the first and 

 second phalanges and are attached to their margins, and weaker 

 portions, opposite the interphalangeal joints, which are attached 

 to the ends of the adjacent phalanges and the margins of the 

 plantar accessory ligaments of the joints. The stronger parts 

 are to prevent the tendons springing away from the bones when 

 the joints are flexed, whilst the weaker parts allow the move- 

 ments of the joints to take place. 



Clean the surfaces of at least two sheaths, then open one of 

 them by a longitudinal incision, to display the mucous lining 

 and the two tendons which are enclosed by the sheath. 



The Flexor Sheaths of the Digits and the Insertions of 

 the Flexor Tendons. In each digit an osteo-fibrous canal is 

 formed. It is bounded, dorsally, by the plantar surfaces of 

 the phalanges and the plantar ligaments of the interphalangeal 

 joints, and, plantarwards and at the sides, by the fibrous 

 flexor sheaths. Two tendons enter each canal a tendon 

 of the short flexor of the toe and a tendon of the long flexor. 

 Opposite the posterior part of the first phalanx the short 

 flexor is superficial and the tendon of the long flexor lies 



