REPORT ON THE MARSUPIALIA. 121 



members of the intrinsic group. This is a most useful, and, as a general rule, a most 

 reliable guide in determining the muscles which belong to the plantar layer. He says 

 the deep division " sinks at the outer edge of the contrahentes (i.e., adductors) between 

 these and the interossei. This nerve courses inwards, constantly placed on the interossei 

 and covered by the contrahentes and giving branches to both groups." Now in Man this 

 nerve passes inwards superficial to the plantar interossei and under cover of the adductor 

 obliquus hallucis, thus cutting them off from each other. 



(4.) In a foot dissected in the Practical Anatomy Rooms of the University of Edin- 

 burgh this summer session (18S1), I observed a distinct fleshy slip proceeding from 

 the outer edge of the adductor obliquus hallucis to be inserted into the outer side 

 of the base of the first phalanx of the index. This clearly represented the adductor 

 indicis. 



The flexor brevis minimi digiti is a single-headed muscle which is inserted into " the 

 base and external border of the first phalanx of the little toe " (Quain). I believe that the 

 third plantar interosseus is the inner head of this muscle. 



Fig. 2. Schematic view of the intrinsic muscles of the left human foot— seen in transverse section through the meta- 

 tarsus. The lost elements are sketched in dotted outline. Compare with figure 3. 



(/') Flexor brevis hallucis. (/ 3 1) Tibial head of flexor brevis medii (1st plantar interosseus). (/ 4 t) Tibial head ot 

 flexor brevis annularis (2nd plantar interosseus). (/ 5 t) Tibial head of flexor brevis minimi digiti (3rd plantar 

 interosseus). (/ 6 /) Fibular head of flexor brevis minimi digiti. (p 1 ) Adductor obliquus hallucis. (d 1 ) Ab- 

 ductor hallucis. (d 6 ) Abductor minimi digiti. (d 2 to d 5 ) Dorsal interossei. (I. to V.) Metatarsal bones. 

 (e.p.n) External plantar nerve giving off its superficial and deep division. 



The remaining two plantar interossei (viz., the second and first) are the flexores 

 breves of the annularis and medius, which have lost their outer heads, and have taken on 

 an adducting action in consequence, antagonising in this respect the action of the fourth 

 and third dorsal interossei. 



Nor need we consider this change of function remarkable when we have already 

 seen in the Horse a short flexor converted into a powerful ligament ; in the Sloth 



(ZOOL. CHALL. EXP.— PART XVI. 1882.) Q 16 



