. Elements of comparative zoology. Zoology. VER TEBRA TES. 293 region, the vertebra of which is connected with the bones (girdle) supporting the hind limbs. In the higher verte- brates the trunk vertebra can be divided into thoracic and lumbar regions, the former with, the latter without, ribs. As we have just seen, there may be two kinds of ribs— those of fishes and those of the higher vertebrates. In reptiles, birds, and mam- mals the ribs of one side fuse at their ven- tral ends with their fellows of the opposite side. The fused regions separate from the ribs and unite together, giving rise
. Elements of comparative zoology. Zoology. VER TEBRA TES. 293 region, the vertebra of which is connected with the bones (girdle) supporting the hind limbs. In the higher verte- brates the trunk vertebra can be divided into thoracic and lumbar regions, the former with, the latter without, ribs. As we have just seen, there may be two kinds of ribs— those of fishes and those of the higher vertebrates. In reptiles, birds, and mam- mals the ribs of one side fuse at their ven- tral ends with their fellows of the opposite side. The fused regions separate from the ribs and unite together, giving rise to the breast-bone or sternum (fig. 103). In some sterna the separate elements can be traced; in others the fusion is complete. The sternum in the Amphibia has no con- nection with the ribs, and may therefore be different from the breast-bone in the Sauropsida and Mammalia. The skull consists of two portions: the . , . r . Fig. 103. — Ster- cranium and the face, or better, the vis- ceral skeleton. The former affords pro tec- elements of which . , ' , it is composed. tion to the bram and support to the organs of sense; the visceral portions cluster around the mouth, nose, and throat. In the sharks the cranium is a continuous box of carti- lage, only perforated for the passage of nerves and blood- vessels. In the other vertebrates some or all of this carti- lage becomes replaced by bone, either by direct conversion (ossification) or by substitution. The bony cranium (un- like the cartilaginous cranium) is not a continuous wall, but is composed of separate bones firmly united together, the number varying between wide limits, being most. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
Size: 949px × 2635px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
