Hymenochirus is further remarkable for the presence of only six distinct pieces in the vertebral L C FIG.
Vertebral column composed of about 50 vertebrae, viz.
The scapula is sabre-shaped, and extends backwards over the ribs, lying almost parallel to the vertebral column.
This is the most perfect arrangement attained by the vertebral column, and is typical of, and restricted to, birds.
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.
The Sympathetic System forms a chain on either side of the vertebral column.
Each brachiocephalic soon sends off its subclavian, while in the normal or more usual cases the rest proceeds as the carotid trunk, inclusive of the vertebral artery.
Every "line" of its build is designed and eminently adapted for rapid progression through the water; the muscles massed along the vertebral column are enormously developed, especially on the back and the sides of the tail, and impart to the body a certain rigidity which interferes with abruptly sideward motions of the fish.
LAMPREY, a fish belonging to the family Petromyzontidae (from r rpos and Ww, literally, stone-suckers), which with the hag-fishes or Myxinidae forms a distinct subclass of fishes, the Cyclostomata, distinguished by the low organization of their skeleton, which is cartilaginous, without vertebral segmentation, without ribs or real jaws, and without limbs.
In the dorsal fin they have from 17 to 20 rays, and in the anal fin from 16 to 18; there are from 53 to 59 scales in the lateral line and 54 to 56 vertebrae in the vertebral column.
The neck is long and curved, and its vertebrae are remarkable for the position of the canal for the transmission of the vertebral artery, which does not perforate the transverse process, but passes obliquely through the anterior part of the pedicle of the arch.
It may be added that in the Oreodontidae the vertebral artery pierces the transverse processes of the cervical vertebrae in the normal manner.
This notochord represents the persistent primordial skeletal axis which, in the higher Craniata (though not so in the lower), gives way by substitution to the segmented vertebral column.
Traquair in 1890, in allusion to its well-developed vertebral rings; and its structure was studied in detail in 1903 by Professor and Miss Sollas, who succeeded in making enlarged models of the fossil in wax.
The vertebral axis shows a series of broad rings, with distinct neural arches, but no ribs.
The marked curvature of the vertebral column, by breaking the shock to the neck and head in running and leaping, likewise favours the erect position.
The vertebral column of the gorilla differs from that of man in its curvature and other characters, as also does the conformation of its narrow pelvis.
As to the vertebral column and pelvis, the lower apes differ from the gorilla as much as, or more than, it differs from man.
The vertebral column is almost entirely welded into a solid tube, but there is a complex joint at the base of the neck, to allow the head being retracted within the carapace.
- A vertebral arm-ossicle (fused ambulacrals) of a Zygophiuran, Ophiolepis.
A difficulty naturally arises with regard to the fact that in reptiles the occipital condyle by which the skull articulates with the vertebral column is single, although composed of three elements, whereas in amphibians and mammals the articulation is formed by a pair of condyles.
The vertebral column consists of seven cervical, eighteen dorsal, six lumbar, five sacral, and fifteen to eighteen caudal vertebrae.
However, owing to the evolution of the vertebral column in various directions, and to the inconstant state of things in certain annectent groups, it is not possible, it seems, to apply the vertebral characters to taxonomy with that rigidity which E.
C. Labyrinthodonta, with simple biconcave vertebral disks, very slightly pierced by a remnant of the notochord and supporting the loosely articulated neural arch.
This condition is derived from (Outline after Jaekel.) that of the Rhachitomi, as shown by the structure of the vertebral column in young specimens.
- Vertebral and ventral (B) views of the sacral column of Hymeno- vertebrae (S.V.); S.R.', S.R.
Gadow, "On the Evolution of the Vertebral Column of Amphibia and Amniota," Phil.
(23) "On the Development of the Vertebral Column in Pipa and Xenopus," Anat.
Notwithstanding the origin of organs, it still for a certain time, by reason of its want of an internal bony skeleton, remains worm and mollusk, and only later enters into the series of the Vertebrata, although traces of the vertebral column even in the earliest periods testify its claim to a place in that series."