A manual of the anatomy of vertebrated animals / by Thomas H. Huxley.

  • Thomas Henry Huxley
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: A manual of the anatomy of vertebrated animals / by Thomas H. Huxley. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    while the corresponding surface of the leg looks backwards and upwards, and the ungual phalanges are turned back- wards. The chief modifications of the manus and pes arise from the excess, or defect, in the development of particular digits, and from the manner in which the digits are con- nected with one another, and with the carpus or tarsus. In the Ichthyosauria and Plesiosauria, the Turtles, the Cetacea and Sirenia, and, in a less degree, in the Seals, the digits are bound together and cased in a common sheath of integu- ment, so as to form paddles, in which the several digits have little or no motion on one another. The fourth digit of the manus in the Pterosawria, and the four ulnar digits in the Bats, are vastly elongated, to support the web which enables these animals to fly. In existing birds the two ulnar, or post-axial, digits are aborted, the metacarpals of the second and third are ankylosed to- gether, and the digits themselves are inclosed in a common integumentary sheath; the third invariably, and the second usually, is devoid of a claw. The metacarpal of the pollex is ankylosed with the others, but the rest of that digit is ] free, and frequently provided with a claw. Among terrestrial mammals, the most striking changes of the manus and pes arise from the gradual reduction in the number of the perfect digits from the normal number of five to four (Sus), three (Rhinoceros), two (most Buminantia), or one (Equidce). The Pectoral and Pelvic Arches.—The proximal skeletal elements of each pair of limbs {hvmeri or femora) are supported by a primitively cartilaginous, pectoral, or pelvic girdle, which lies external to the costal elements of the vertebral skeleton. This girdle may consist of a simple cartilaginous arc (as in the Sharks and Rays), or it may be complicated by subdivisions and additions. The pectoral arch may be connected with the skull, or with the vertebra] column, by muscles, ligaments, or dermal ossifications, though, primitively, it is perfectly free from
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