REPORT ON THE MARSUPIALIA. 65 



Flexor brevis hallucis (fig. 3,/ 1 ). — The two bellies of this muscle are separated by the 

 tendon of the flexor longus hallucis. They have a common origin from the thickened 

 part of the plantar cartilage close to the base of the first metatarsal bone. Each belly 

 is joined by the abductor and adductor respectively, and is inserted one into the inner 

 sesamoid bone and the other into the outer sesamoid bone at the base of the first 

 phalanx of the hallux. 



The succeeding three flexores breves (fig. 3,f 2 to / 4 ), viz., for the index, medius, and 

 annularis present the usual arrangement. That for the annular digit, however, is the 

 strongest of the series, seeing that it is in connection with the longest toe. Both bellies 

 of this muscle arise from the base of the third metatarsal bone, and therefore they 

 lie obliquely in the sole. This muscle also differs from the other members of the series 

 in being inserted not only into the sesamoid bones but likewise into the extensor tendon. 



The flexor brevis minimi digiti (fig. 3,f 5') is represented merely by a slender tibial 

 head which arises by a long tendon from the cuboid bone. The fibular head is insepar- 

 ably united with the opponens minimi digiti. 



Dorsal layer (d 1 to d 6 a.m). — This layer is represented by only four muscles. 



1. The abductor hallucis (d 1 ). 



2. The abductor minimi digiti (d 6 ). 



3. The abductor ossis metatarsi minimi digiti (a.m). 



4. The abductor indicis or first dorsal interosseus (d 2 ). 



The abductor hallucis arises from the inner margin of the cartilaginous portion of the 

 plantar fascia and is inserted into the tibial side of the first phalanx of the hallux in 

 conjunction with the inner head of the flexor brevis of the same toe. 



The abductor minimi digiti takes origin from the inferior surface and outer border of 

 the os calcis. It likewise receives a small separate slip from the plantar cartilage. The 

 fleshy belly of the muscle soon ends in a long tendon which is inserted into the outer side 

 of the proximal extremity of the first phalanx of the minimus. In all probability the 

 small fasciculus which is derived from the plantar cartilage represents the third factor of 

 the abducting apparatus on the outer margin of the foot. 



The abductor ossis metatarsi minimi digiti arises from the os calcis in common with 

 the preceding muscle. It has the usual insertion into the base of the fifth metatarsal 

 bone immediately under that of the peroneus brevis. 



The abductor indicis consists of fibres which extend between the adjacent margins of 

 the first and second metatarsal bones. It also arises by a long narrow tendon which bes 

 under cover of the flexor brevis hallucis and springs from the tibial side of the base of 

 the metatarsal bone of the hallux. The muscle is inserted mainly into the inner aspect 

 of the base of the first phalanx of the index, but some fibres are likewise inserted into 

 the hallux along with the adductor hallucis. 



(ZOOL. CHALL. EXP. PART XVI. — 1882.) Q 9 



