J. Playfair MeMurrich - 485 
bundle which forms the radial border of Brooks’ adductor having its 
origin from the fascia covering the first and second metacarpals decid- 
edly proximal to the origin of the adductor and being overlapped, fur- 
thermore, on its ulnar border by the adductor. In accordance with 
Young’s description of the adductors then, there is a large fan-shaped 
adductor pollicis (Fig. 7, ad p) and a similar adductor minimi digiti 
(adm) which arise mainly from a median fibrous raphe in the line of 
the middle metacarpal and insert into the ulnar and radial sides respec- 
tively of their digits. In addition there are two other adductors 
(ad*), much less extensively developed, arising from the dorsal sur- 
face of the adductor raphe and inserting into the ulnar and radial sides 
respectively of the second and fourth digits. 
In the cat the correct interpretation of the deeper muscles of the 
hand is rendered difficult by the flexor brevis profundus elements being 
pushed volarly so that some of them come to lie in apparently the 
same plane as the adductors and are, furthermore, traversed near 
their volar surface by the deep branch of the ulnar nerve, thereby 
seeming to be partly epineural structures. If, however, these two 
peculiarities be taken into consideration, an arrangement of the various 
portions of the flexor brevis medius and profundus essentially similar 
to what occurs in the opossum and the mouse can be made out. 
Tt is the profundus portion for the index (Fig. 8, fbp.and fbp;) 
which is especially obtrusive in the way mentioned, occupying a posi- 
tion so far volar as to separate the adductor pollicis from the adductor 
indicis. The former of these muscles arises from the surface of the 
os magnum and is inserted into the ulnar side of the proximal pollical 
phalanx, while the latter (Fig. 8, ad’) arises in continuity with the 
rest of the adductor layer from the fascia covering the volar surface 
of the carpal bones and the bases of the metacarpals and is inserted 
into the ulnar side of the base of the proximal phalanx of the index. 
In addition to these two muscles there are two others belonging to the 
adductor layer; they arise together and are closely associated through- 
out the greater part of their course, the more ulnar one (ad m’), how- 
ever, inserting into the radial side of the shaft of the fifth metacarpal, 
while the more radial one (adm) passes to the base of the proximal 
minimal phalanx. I suspected at first that the more radial of these 
muscles belonged to a different layer than the other, but the evidence 
available makes it preferable to regard the two together as equivalent 
to the adductor minimi digiti of the opossum whose insertion has been 
partly extended proximally upon the metacarpal. 
In the mouse three muscles may be recognized as belonging to the 
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