6i6 HUMAN ANATOMY. 



The two sacs occasionally communicate with each other. On account of the density 

 of the annular ligament, the distention has a central constriction and expansions in 

 the palm and above the wrist, — " hour-glass shape." These tendons also are often 

 involved in fractures of the lower end of the radius, although, on account of the fact 

 that the extensors are in closer relation to that bone than is the deep flexor, and 

 that the other flexors — excepting the longus poUicis — are still farther separated from 

 it, limitation of their motion is neither so frequent nor so marked. 



In the palm of the hand the thenar and hypothenar eminences are covered in 

 by their fasciae, which separate them from the central space of the palm through 

 which the flexor tendons run, and over which is spread the fan-shaped, deep palmar 

 fascia, beginning at the tendon of the palmaris longus above, and spreading out to 

 be divided below into the slips for the fingers (Fig. 587). Transverse fibres unite 

 and strengthen these slips, which send fibres also to the sheaths of the flexor tendons 

 and to the skin. 



It may be noted here that progressive muscular atrophy usually begins in the 

 hand muscles, affecting first those of the thenar, then those of the hypothenar emi- 

 nence, and next the interossei. When the latter are greatly wasted the hand assumes 

 the appearance of a bird's claw, — the main en griff e (Duchenne). 



Dupnytren s contractioi affects chiefly the digital prolongations of the palmar 

 fascia, although it extends secondarily to the bundles of fibres uniting the skin and the 

 aponeurosis. It begins usually as a dense thickening of the fascia near the line of 

 the metacarpo-phalangeal articulation. It extends in both directions, the concomitant 

 shortening slowly drawing down first the distal and then the intermediate phalanx. 

 The skin becomes closely adherent to the contracted fascia. The condition is seen 

 oftenest in hands subjected to frequent slight traumatism, as in laborers, or in those 

 of gouty or rheumatic persons past middle age. 



Beneath the flexor tendons, and above the interossei, the metacarpal bones, and 

 the radial arch, lies another layer of fascia (interosseous) which resists but feebly 

 the passage of pus towards the dorsum of the hand. It is connected with the thenar 

 and hypothenar fasciae. 



Several varieties of palmar abscess have been described (Tillaux) in accord- 

 ance with the original site of the infection, the spread of which will be determined by 

 the above-mentioned anatomical considerations, {a) Infection just beneath the 

 thick epidermis causes a superficial pustule or abscess (subepidermic) which, if 

 promptly and freely opened, gives rise to no difficulty. (b) Infection beneath the 

 skin (subdermic) is attended by more pain, and, if neglected, may penetrate the 

 aponeurosis ; but it is separated by that structure from the synovial sheaths and 

 cavities ; it may be widely opened with no reference to the latter or to vessels ; it is 

 accompanied by little or no swelling on the dorsum ; it has no tendency to extend up 

 to the wrist ; movements of the fingers are not very painful, {c) Subdermic infec- 

 tion beginning .in the spaces just above the interdigital clefts {i.e., between the 

 digital slips of the palmar fascia) may extend by continuity of connective tissue very 

 rapidly to the dorsum of the hand, which may then appear to be the chief seat of the 

 infection ; the syrnptoms are relatively mild, as the toxic exudate is not under great 

 pressure. {d) Subaponeurotic infection — true palmar abscess — is excessively 

 painful, extends rapidly to the dorsum by perforating the interosseous fascia, and 

 often to the front of the wrist and forearm by following up the flexor tendons ; move- 

 ments of the fingers are painful ; the dorso-palmar diameter of the hand is vastly 

 increased ; the constitutional symptoms are often marked. 



Such abscess may also point just above the interdigital webs or near the ulnar or 

 radial borders of the hand. Early incision is imperative and, if made over the line of 

 a metacarpal bone and limited in an upward direction by a transverse line correspond- 

 ing to that of the web of the fully extended thumb (to avoid the digital vessels and 

 palmar arches), may be made freely. Above the wrist the region of safety is just to 

 the ulnar side of the palmaris longus. 



On the fingers the skin resembles in its characteristics that of the hand. On the 

 palmar surface of the first and second phalanges the skin and the subcutaneous fat are 

 connected with the dense fibrous sheath of the flexor tendons by vertical connective- 

 tissue fibres, and at the level of the joints — where the sheaths are lax and thinner — 



