166 SURGICAL ANATOMY OF THE PALM. 



theca of the flexor tendons, an osseo-fibrous canal, 

 formed by the phalanges and a dense tube of fibrous 

 tissue, disposed in circular and oblique bands, very thin 

 immediately opposite the flexures, and perforated at the 

 roots of the fingers for the passage of vessels and cellular 

 tissue. The sheath is very thin on the palmar aspect of 

 the ungual phalanx, and purulent infiltration into it is 

 common at this point. The flexor tendons which lie in 

 the sheath, are those of the flexor sublimis (perforates) 

 attached by two slips to the sides of the second pha- 

 langes, and those of the flexor profundus (perforans) 

 which divides them, and is inserted into the base of the 

 ungual. The canal is lined with a synovial membrane, 

 which is reflected on to the tendons. Slender tendinous 

 filaments, called vincula, connect these tendons to the 

 walls of the canal. On the dorsum there is a strong 

 aponeurosis formed by the extensor tendons, further 

 strengthened by the expansion of the interossei and 

 lumbricales. The common extensor passes on to the 

 second phalangeal articulation, opposite which it divides 

 into three fasciculi, the central one being inserted into 

 the base of the second phalanx, whilst the two lateral 

 slips reunite and pass on, to be inserted into the base of 

 the ungual. 



In excision of the phalangeal articulations it is neces- 

 sary to retain as much as possible of this dorsal aponeu- 

 rosis, in order that the power of extension may be after- 

 wards kept. In disarticulation of a phalanx, it must be 

 remembered that immediately the lateral ligament is 

 divided the joint is opened, and that this lateral liga- 

 ment does not coincide with the palmar fold of the digit, 

 but is a little in front of it, so that the guide for enter- 



