vi n.J THE MUSCLES. 359 



The abductor digiti minimi may be absent, as in many 

 forms, e.g. the Horse; or it may be very large and aided, as in 

 Lemur, by another muscle (which is generally absent in man) 

 called abductor ossis metatarsi quinti, and which, arising 

 from the calcaneum, is inserted into the fifth metatarsal. 



Flexor accessnrius (Fig. 319). This may be altogether 

 wanting, not only in such forms as the Horse, but even in 

 members of man's order, e.g. Lemur. It may be inserted by- 

 muscular fibre into the perforating flexor tendons, or it may 

 furnish most of the long flexor tendons, as in Hapale. It 

 is a more constant muscle than might be expected, as it is 

 to be found in the Iguana. It may be enormous, with three 

 fleshy bellies, as in the Three-toed Sloth. 



Liimbricales (Fig. 317). These muscles may be quite 

 absent, as in the Hedgehog, Seal, and Three-toed Sloth, and 

 in Birds. They may be represented by tendons only, as in 

 the Horse. They may be only two in number, as in the 

 Agouti and Hyrax ; or they may be as many as six or seven 

 in number, as in Bats. They are more constant structures 

 than might have been expected, as they are found in Reptiles, 

 e.g. in the Iguana and Chameleon, and in the Frog, though 

 they do not seem to be developed in Tailed- Batrachians. 



Flexor brevis pollicis pedis. As need hardly be said, this 

 muscle may be entirely absent. It may, however, reappear 

 when wanted, low down in the scale, e.g. in Chamceleo 

 Parsonii and the Frog. 



The adductor pollicis pedis may perhaps be represented 

 in the Frog by a large muscle taking origin between the 

 elongated tarsal bones ; but it is inserted into the naviculare 

 and accessory tarsal ossicle. 



Transi'ersus pedis. This may be larger relatively than in 

 man, as in the Apes. It may be blended with the muscle last 

 noticed, as in Lemur, and it may, as in many forms (e.g. 

 the Horse) be absent altogether. Muscular fibres may be 

 inserted into the metatarsal of the hallux, thus forming an 

 opponens hallucis, as in the Orang ; and a similar structure 

 may be still further developed in a singularly low form, 

 i.e. the Frog, where an opponens muscle is supplied to each 

 of the four inner digits, and this in addition to transversi 

 muscles, which extend between the first and second, second 

 and third, and third and fifth digits respectively. 



A flexor brevis digiti minimi pedis may be present, as in 

 Apes, or it may be absent, as in many forms. It exists in 

 the Iguana (Fig. 317) and Chameleon. In addition to this 



