THE EXTREMITIES OF ORYCTEROPUS CAPEXSIS. 58 



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unciform bone, and is inserted, a sesamoid ossicle intervening, into the base of the 



proximal phalanx of the "little" digit. Some fibres, 100, join the tendon of the inner- 

 most of the superficial interossci. 



Interossci.— These muscles, to avoid confusion as much as possible, are, I think, better 



divided into superficial and deep, than into palmar and donal interossci. There are 



only two superficial muscles, which cross each other like lite upper arms of an \ and 



seem to correspond to two out of the three muscles described by Prof. Humphry as 



"palmar" interossei\ 



The one which passes to the " little" digit are j from the ulnar half of the palmar 



ligament, immediately anterior to the front margin of the unciform bone. It is a fan- 

 shaped muscle ; and its fibres radiate towards a Hat tendon, which, i tssing along the 

 radial side of the little digit, joins that branch of the extt <or < mmunia which is sent 

 to this di<?it. On becoming tendinous it is joined by a slender offset from the abductor 



dig 

 The other superficial 



d bv, and arises alittl- in advance of. 



preceding, from the palmar ligament at the neighbouring parte of the bases of the meta- 

 carpals of the third and fourth digits. After widening a little from it» origin, it again 

 gradually contracts, and joins, through the medium of its tendon, the tendon of tin- 

 deep interosseus which passes to the ulnar side of the index. 



When these two muscles act in concert, they mu t stromrly adduct the outermost and 

 innermost digits towards the middle line of the hand. 



Deep interossci.— To facilitate description, it had better first be stated that each digit 

 has a strong ligament, oblique in direction, attached, at one extremity, to the ulnar sid- 

 of the base of its metacarpal, at the other, after previously forking, into the sesamoid at 

 the base of its proximal phalanx. The deep interossci have great extent of oriuin from 

 these ligaments, which may conveniently be termed " metacarpal " ligaments, and from 

 eacb of which a pair of the above muscles arises, those taki g omin from the radial 

 sides passing to the radial, those from the ulnar passing to the ulnar sides of their 



corresponding digits 



The radial interosseus of the index has two heads of 



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fusiform, bj 



tendon, from the anterior edge, palmad, of the scaphoid, the other from the radial Bide 

 of the metacarpal ligament of the index. These, after junction, become tendinous ; and 

 their tendon joins the branch of the extensor commu s sent to the index. The ulnar 



of this digit arises from the inner side of its metacarpal lig 



fter 



becoming tendinous, sends an offset to the sesamoid bone, is joined by the radial of the 

 two superficial interossci, and passes to the expansion of the common t tensor tendon 

 over the proximal phalanx. This muscle may, I think, be termed conveniently, if not 

 homolo-ically, "abductor indicis." The - middle" and « fourth" digits have each a 



deep interosseus on either side. From the obliquity of the metacarpal ligaments of 

 index and two succeeding digits, the muscles on the radial sides seem to have a much 

 more strictly palmar origin than their fellows on the ulnar sides— these latter being 

 almost hidden, when the digits are closely approximated, in the intermetacarpal spaces. 



1 Loc. cit. p. 305. 



