47 
upon the pollex, index, and medius; hence Meckel’s name for it of 
extensor pollicis et digiti indicis. 
I have satisfied myself by dissection that the accounts given by 
Meckel and more fully by Dr. Brooks are correct descriptions, and 
there can be little doubt that the muscles are correctiy named in their 
writings. It may be remarked that the quite superficial fleshy and 
aponeurotic origin from the ulna of the extensor pollicis et indicis 
reminds one of the origin of the human extensor carpi ulnaris. Here, 
however, the resernblance ends. It may also be noted that in Echidna 
the ulnar origin of the former muscle is not superficial, as it is in 
Ornithorhynchus, being overlapped by the olecranon fibres of the 
extensor carpi ulnaris, which he close up to the posterior border of the 
ulnar shaft. Accordingly, there is a superficial resemblance between 
the ext. carpi ulnaris in Hchidna and the extensor pollicis et indicis in 
Ornithorhynchus, so far as the relations of their fleshy bellies are con- 
cerned; but the homologue of the latter muscle in Echidna will be 
found beneath the former. 
In Chlanvydophorus* the muscle is very weak, ectocondylar in origin, 
and inserted into metacarpal V. 
In Orycteropus,t origin ectocondylar, insertion by two slips into 
metacarpals [V. and V. 
In Dasypus sexcinctus,t ectocondylo-ulnar in origin, insertion V. 
metacarpal. 
In Bradypus gularis§ two muscles are present; one ectocondylar 
inserted into metacarpal IV., the other, ectocondylo-ulnar (mainly 
ulnar) in origin, inserted into metacarpal V. 
In Cyclothurus,§ also two muscles; one ectocondylar only, inserted 
inte metacarpal III.; the other, ectocondylo-ulnar (mainly ectocon- 
dylar), inserted chiefly into metacarpal V., but sending a delicate slip to 
metacarpal IV. 
In Manis,§ also two muscles; one, ectocondylo-ulnar in origin, is 
the smaller, and is inserted into the palmar surface of metacarpal V.; 
the other—more internal—arises from the ectocondyle, “between the 
preceding and the extensor communis, and divides a little above the 
wrist into two broad tendons; the outer and smaller of these is in- 
serted into the outer side of metacarpal V., and the inner is continued 
along the outer side of digit IV. to the terminal phalanx.”?’ Humphry 
remarks in reference to this arrangement that the three elements just 
described in /anis correspond to the peronei in the hind limb, and 
he proceeds—“ In the forelimb the three muscles are in several ani- 
mals blended into one, the extensor carpi ulnaris. In others there are 
two—the extensor carpi ulnaris, constituting the homologue of the 
peroneus brevis and longus, and the extensor minimi digiti, which may 
pass to two or more digits, constituting the homologue of the peroneus © 
tertius. All these, together with the extensor digitorum, belong to 
what I describe as the ‘superficial layer.’’’|| Against this view St. 
John Brooks maintains that the extensor minimi digiti appertains not 
to the superficial stratum at all, but to the deep or extensor brevis 
stratum, such as is found in Hatteria. Upon this question c.f. Brooks’ 
papers and discussion on his views.{ 
* XXVIL, page 257. fxv., page 583. txiv., page 543. § xxii., page 46. 
XXll., page 46. 4i., pp. 1 e¢ seq., and Ixxii., pp. xv. and xix. 
