. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. LIMBS 161 Fe- FL Round a centra/e, which may be double, is arranged a series of other elements, of which three are proximal, and a varying number (four to six) distal. The proximal, in correspondence with their relations to the bones of the fore-arm and shank respectively, are spoken of as radiale or tili't«l<', ulnare or fibula re, and intermedium ; while the distal are called carpalia or tarsalia (in the narrower sense). They are counted beginning from the pre- axial (radial or tibial) side of the limb. Amphibians. —
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates. LIMBS 161 Fe- FL Round a centra/e, which may be double, is arranged a series of other elements, of which three are proximal, and a varying number (four to six) distal. The proximal, in correspondence with their relations to the bones of the fore-arm and shank respectively, are spoken of as radiale or tili't«l<', ulnare or fibula re, and intermedium ; while the distal are called carpalia or tarsalia (in the narrower sense). They are counted beginning from the pre- axial (radial or tibial) side of the limb. Amphibians. —The anterior and posterior extremities of Urodela are formed essentially on the ground-plan described above, but more or fewer of the carpals or tarsals may undergo fusion. In them, as in Anura, there are five digits in the hind-limb, and usually only four in the fore- limb. In the Anura the radius and ulna become united, and a separate intermedium is not re- cognisable; the proximal row of the tarsus, more- over, consists of only two cylindrical bones, one of which (astragalus) corre- Fl(1 sponds to a tibiale, and the other (cakaneum) to %, + digits ^/V-.^femur; Fi^, fibula; a fibulare (Fig. 124). In the distal row of the carpus four separate elements are formed in Anura, but this number may become reduced owing to secondary fusion; in rare cases a fifth carpal may also be present. Tarsalia // and /// are the most constant elements, but even these may undergo fusion, and tarsalia /Fand Fare generally represented by a In Anura the metat:\rsals and phalanges, between which the web of the foot is stretched, are, like the proximal tarsals, very long and slender. The femur, as well as the fused bones of the 1 Very different views are held with regard to the homologies of the individual carpals and tarsals in Amphibians, and the older numbering and nomenclature are therefore provisionally retained here. M. ^ 1-23.—HIND LIMB OF A URODKLE (Spderpes fuscus). , meta- tar
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