158 COUES, 



same aspect of the palm, and distinctly inserted into the front of 

 the base of the first phalanx of the thumb. This muscle is single, and 

 not separable into adductor, abductor, etc. ; but on the hypothenar 

 side we find what we take to be both these muscles acting upon the 

 little finger. An abductor (or short flexor?) arises rather broadly from 

 the outer side of the pisiforme, and runs along the ulnar aspect of 

 the fifth metacarpal, to a little beyond the base of the first phalanx 

 of the little finger, where its tendon is lost in the digital sheath. 

 An adductor is smaller, a mere thread, arising from the centre of the 

 palm, and running along the inner side of the fifth metacarpal to ter- 

 minate opposite the other on the side of the little finger. 



In this animal, the thumb cannot be distinguished by any function 

 that it has from the little finger; nor by any intrinsic physical 

 character, except its being only two- instead of three-jointed; and 

 the special muscles of these two digits are nearly identical. In 

 " archetypal " condition we hold these digits to be physically identi- 

 cal, and their subsequent differentiation in mobility, direction of axis, 

 number of joints, and muscles acting upon them, to be purely teleo- 

 logical. Originally we may perhaps hold the thenar and hypothe- 

 nar muscles to be modified interossei, and to be represented each 

 by a single muscle ; though as a matter of fact we ordinarily have, 

 from two to four (most commonly three ; an adductor, abductor, and 

 flexor brevis) muscles into which each interosseus may have been 

 differentiated. It is interesting to observe, that in this case of the 

 Ornithorliynchus, with thumb and. little finger so similar, as far as func- 

 tion is concerned, what little difference in the number, etc., of spec- 

 ial muscles there is, is in the favor of the little finger, a condition the 

 reverse of usual. 



Interossei. Each of the digits except the two lateral ones has a 

 palmar interosseus; the three are quite similar. They arise almost 

 together from the middle of the palm, and divaricate thence upon the 

 second and fourth fingers. They lie directly upon the palmar aspect 

 of the metacarpals and proceed to split upon the basal phalanges of 

 the fingers, terminating on either side on the digital sheaths. The 

 dorsal are faintly developed. 



IX. MUSCLES CONNECTING THE PELVIS WITH THE BODY. Only one 

 muscle actually passes from the body to be " inserted " in the pelvis, 

 and this, in its action at any rate, is rather a muscle of the back. The 

 numerous other body-muscles that have pelvic attachment, are only 

 incidentally, as it were, connected with that arch? and really belong 

 elsewhere, as to abdomen, perinseum, etc. 



Psoasparvus. Large, much exceeding the other. It arises from 

 vertebral centra (except the last two lumbar) up to about the eighth 



