Elements of the comparative anatomy of the vertebrate animals designed especially for the use of students / by Rudolph Wagner ; Edited from the German by Alfred Tulk.

  • Rudolf Wagner
Date:
1845
Catalogue details

Licence: Public Domain Mark

Credit: Elements of the comparative anatomy of the vertebrate animals designed especially for the use of students / by Rudolph Wagner ; Edited from the German by Alfred Tulk. Source: Wellcome Collection.

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    Cheiroptera, Solidungula, and Pachydermata, and some few genera from the other orders, of a single piece, as in Man, both halves having become united in the median line at an early period before or after birth. In other animals both the halves remain perma- nently separated, and are held together only by ligamentous fibres. The lower jaw is in its simplest condition in Balena, where it re- sembles a rounded arched rib. In the Dolphin it is somewhat deep- er, and provided with a small coronoid process. The ascending ramus of the jaw, which is more or less conspicuous in the higher orders of Mammalia, is frequently altogether wanting, as in Oryc- teropus. The Carnivora have a strong and broad, the Ruminantia, as the Camel, a long and small coronoid process. ‘The lower border of the symphysis is in Man alone curved forwards and upwards, in all the Apes it slopes downwards and backwards. Many Mammalia, such as the Carnivora and Rodentia, have a process directed back- wards from the angle of the jaw, a structure which is very generally met with in Birds. The form of the articulating condyle is subject to great diversities, which usuaily characterise entire orders. Thus it is very small, and plays freely in all directions within a shallow glenoid cavity in the Ruminantia; it is much elongated transversely, and locked in a deep cavity of a corresponding form in the Carni- vora so as to admit of no lateral motion; it is lengthened out from back to front, and chiefly moveable in this direction in the Roden- tia. Viewed as a whole, the form of the skull departs most from that of Manin the lowest orders. Thus in the Cetacea the jaws are generally lengthened out in the shape of a snout; and the cranial bones are united merely by squamous sutures. A want of lateral symmetry occurs also in this order. In the Physeter the right na- sal orifice is much the larger, the nasal partition is pushed to the left side, and the nasal bones lie rather behind than by the side of each other. In the Dolphin this asymmetrical condition is extended to other bones, namely, the intermaxillaries. In the Narwhal the lower jaw itself is asymmetrical, the left half like the corresponding half of the upper jaw being the larger and broader. The skull of the Monotremata (Ornithorynchus, Echidna) is very bird-like through the early coalescence of its bones, and the snout-shaped jaws. In the higher orders the facial and maxillary bones con- stantly retreat further backwards. In the Horse the facial is four times larger than the cranial portion of the skull, a proportion ex- actly the reverse of that of Man. The depressions within the
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