. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. LIMBS 127 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. Amphibia.—The anterior and posterior extremities of Urodela are formed essentially on the ground-plan described above. There are usually five digits in the hind-limb, and always four in the fore-limb. In the Anura the radius and ulna become fused together, and a separate intermedium is wanting; the proximal row of the tarsus, moreover, consists of only two cylindri
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. LIMBS 127 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. Amphibia.—The anterior and posterior extremities of Urodela are formed essentially on the ground-plan described above. There are usually five digits in the hind-limb, and always four in the fore-limb. In the Anura the radius and ulna become fused together, and a separate intermedium is wanting; the proximal row of the tarsus, moreover, consists of only two cylindrical bones, one of which {astragalus) corresponds to a tibiaie, and the other (calcaneum) to a fibulare.^ In the distal row of the carpus four separate elements are formed, but this number may become reduced owing to secondary fusions ; in rare cases a fifth carpal may also be present. Very different views exist as regards the homologies of the individual carpals of Anurans. In the distal row of the tarsus, tarsalia II and /// are the most constant elements, but even these may undergo fusion; tarsalia IV and V are generally repre- sented by a ligament; and tarsale I usually does not long remain distinct. In Anura the metatarsals and phalanges, between which the web of the foot is stretched, are very long and slender. The femur, as well as the bones of the shank, which are fused together, are also exceedingly long, in correspondence with the mode of pro- gression of these animals. The skeleton D of the extremities is more strongly ossified in Anurans than in Urodeles, in which many of the elements remain cartilaginous. Traces of an extra toe {i^rehalhtx) occur on the tibial side of the tarsus, and in both Urodeles and Anurans indications of an additional pre-axial digit in the manus are occasionally met with. The number of phalanges on the individual digits varies in different Amphibians. Rudiments of the extremities can be recognised externally in embryos of the limbless Gymno
Size: 1302px × 1919px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
