REPORT ON THE MARSUPIALIA. 101 



The meclius and annularis are enveloped in a common sheath of integument, and 

 the weight of the body rests solely upon them. They are quite incapable of any move- 

 ment of abduction and adduction. 



In the Pig's foot a suspensory ligament is derived from members of the intrinsic 

 group of muscles ; but in this case certain of the dorsal interossei are called into 

 requisition. 



Adducting or 'plantar layer. — This layer is represented by two well-marked muscles, 

 viz.: — 



(1) The adductor indicis. (2) The adductor minimi digiti. 



These muscles arise by a common origin from the central part of the base of the 

 metatarsus, and then diverge from each other to reach their insertions. The adductor 

 indicis is inserted into the outer sesamoid at the base of the first phalanx of the index, 

 and also into the extensor tendon ; the adductor minimi digiti is inserted in the same 

 manner upon the inner aspect of the base of the first phalanx of the little toe. 



The deep division of the external plantar nerve disappears under cover of the 

 adductor minimi digiti, and can be traced inwards under the two plantar muscles, 

 as far as the flexor brevis indicis in which it ends. It supplies all the intrinsic 

 muscles. 



Intermediate layer. — Each digit has a flexor brevis, although in no case does this muscle 

 consist of two fleshy heads. 



The flexor brevis indicis is represented by a well-marked fusiform tibial head which 

 springs from the plantar and inner aspect of the base of the second metatarsal bone, and 

 is inserted by a long tendon into the inner margin of the extensor tendon on the dorsum 

 of the first phalanx of the index. In veterinary books (Chauveax, and Gamgee and Law) 

 this muscle is termed a lumbrical and erroneously described as springing from the perforans. 

 The outer fibular head is present in the form of a slender fibrous cord which stretches 

 from the fibrous textures on the base of the third metatarsal bone to the outer sesamoid 

 of the index. 



The flexor brevis medii is a thick fleshy muscle composed of coarse fasciculi, which 

 represent the tibial head alone. It lies upon the plantar face of the third metatarsal, 

 from the base of which it takes origin. Approaching the metatarso-phalangeal joint it 

 ends in a round tendon which is inserted into the inner margin of the extensor tendon on 

 the dorsum of the first phalanx of the medius. A strong fibrous cord extends from the base 

 of the third metatarsal to the outer sesamoid at the base of the same digit. It is difficult to 

 determine whether this represents the outer head of the flexor brevis medii or the third 

 dorsal interosseus (which is also absent) or both. 



In the case of the annularis it is the fibular or outer head of the flexor brevis, which 

 is present, and it presents exactly the same appearance as the preceding muscle. It 



