FASCLE OF THE FOREARM AND HAXI). 231 



of circular fibres, strengthened, however, by longitudinal and oblique fibres 

 descending from the condyloid eminences of the humerus, from the ole- 

 cranon, and from the superficial insertion of the biceps muscle. It is 

 attached along the subcutaneous margin of the ulna, and may be conveniently 

 divided into an anterior and a posterior part. 



The anterior part of the aponeurosis of the forearm is much weaker than 

 the membrane on the posterior aspect of the limb. It is continued below 

 into the anterior annular ligament. In the hollow immediately below the 

 bend of the elbow, it presents a small oval aperture for the transmission of 

 a short communicating branch between the superficial and the deep veins of 

 the forearm. It increases in density towards the band ; and a little above 

 the wrist affords a sheath to the tendon of the long palmar muscle, which 

 passes over the annular ligament to be inserted into the narrow end of the 

 palmar fascia. Several white lines seen on the surface of the fascia mark 

 the positions of the septa between the 'origins of the muscles descending 

 from the inner condyloid eminence, which are continuous with it. Between 

 the superficial and the deep flexor muscles, another layer of fascia is stretched 

 from side to side; it is stronger below than above, where it generally 

 consists of little more than thin connective tissue. 



The anterior annular ligament of the carpus, previously described at 

 p. 144, is continuous at its upper margin with the fascia of the forearm, 

 and receives some fibres from the tendon of the flexor carpi ulnaris : the 

 lower margin is connected with a deep part of the palmar fascia, and gives 

 origin in part to most of the short muscles of the thumb and little finger. 

 This structure may be considered in some measure as a developed portion of 

 the fascia of the wrist, and also as a ligament. 



The posterior portion of the aponeurosis of the forearm, much thicker than 

 the anterior, is intimately connected with the strong septa between the 

 several superficial muscles, and sends off transversely a thin membrane to 

 separate the superficial from the deeper group of muscles. Approaching the 

 back of the wrist, the transverse fibres increase in number and strength, and 

 these, being stretched from the outer margin of the radius on one side to 

 the cuneiform and pisiform bones and the palmar fascia on the other, 

 constitute the posterior annular ligament of the carpus (see p. 144). This 

 structure is attached not only to the points now indicated, but is likewise 

 connected to the several longitudinal ridges on the posterior surface of the 

 radius, and thus converts the intermediate grooves into fibro-osseous canals 

 to lodge the tendons of the extensor muscles. There are six separate spaces 

 so enclosed, and each is lined by a distinct synovial sac. The outermost space 

 corresponds with the groove on the outer side of the radius, and gives 

 passage to the extensores ossis metacarpi and primi internodii pollicis, the 

 next three, placed on the back of the radius, give passage respectively to 

 the two radial carpal extensors, the extensor secundi internodii pollicis, and 

 the common extensor of the fingers, with the extensor indicis accompanying 

 it ; between the radius and ulna is the compartment for the extensor minimi 

 digiti ; and resting in the groove on the back of the ulna is that for the 

 extensor carpi uluaris. 



On the back of the hand there is only a thin layer of fascia prolonged from 

 the posterior annular ligament over the extensor tendons, and separating 

 them from the superficial veins and nerves. Beneath this ure special fibrous 

 membranes stretched over the interossei muscles. 



On the palm of the hand is the palmar fascia, a strong aponourosis, 

 consisting of a central and two lateral portions. The lateral parts are very 



