The vertebrae are stereospondylous, the centrum or body and the arch being com pletely fused into one mass, leaving not even a neuro-central suture.
Sometimes the pad is reduced to a ventral semi-ring or meniscus; it retains its largest almost original shape and size in the second vertebra, the axis or epistropheus, where it forms a separately ossifying piece which connects, and coossifies with, the odontoid process (the centrum of the atlas) and the centrum of the second vertebra.
Dorsal vertebrae frequently have a ventral outgrowth of the centrum; these hypapophyses may be simple vertical blades, I-shaped, or paired knobs; they serve for the attachment of the thoracic origin of the longus collianticus muscle, reaching their greatest development in Sphenisci and Colymbidae.
Like Gloger, Sundevall in his ideal system separated the true passerines from all other birds, calling them Volucres; but he took a step further, for he assigned to them the highest rank, wherein nearly every recent authority agrees with him; out of them, however, he chose the thrushes and warblers to stand first as his ideal " Centrum " - a selection which, though in the opinion of the present writer erroneous, is still largely followed.
Originally of Liberal tendencies, he developed from 1837 onwards ultramontane opinions, founded in 1852 the Catholic group which in 1861 took the name of the Centre party (Centrum) and became one of its most conspicuous orators.
On the 30th of January Bismarck took the opportunity of inveighing against the formation of the sectarian Centrum as being " one of the most monstrous phenomena in the world of politics," and he left no room for doubt in the minds of his hearers that he regarded the leadership of Windthorst as constituting, in his eyes, a peril to the national unity.
This conflict, moreover, brought Ultra montanism the enormous advantage that, even after the abolition of the May Laws, it had still left to it a well-disciplined press, an admirable organization, and a network of interests and interested parties; and all these combined to make the Centrum the strongest and the most influential political party in Germany for the remainder of the 19th century.
Till the year 1863 there had been a small party of Catholics in the Prussian parliament who received the name of the c~tr~ Centrum, from the part of the chamber in which they sat.
In the trunk vertebrae the opisthocoelous character of the centrum graduall y diminishes.
This mode of formation of both the arch and the greater part or whole of the so-called centrum from the same cartilage explains why there is never a neuro-central suture in these batrachians.
(I) Amphicoelous; each end of the centrum is concave; this, the lowest condition, is embryonic, but was retained in Archaeopteryx and in the thoracic vertebrae of Ichthyornis.
Later those pads fuse with the anterior end of the centrum of the vertebra to which they belong; where the vertebral column is rendered inflexible, the disks are ossified with the centra and all trace of them is lost.