. Zoology : for students and general readers . Zoology. Mid brain. NEBVOUa SYSTEM OF VERTEBRATES. 393 {Optic lobes, corpora bigemlna or qaadrigemina (tnesen- cepbalon). Crura cerebri. Optic ventricle or Iter a tertio ad quartum ventriculum. Hind brain. Cerebellum (with its ventricle and the pons varolii, form- ing the metencephalon). Medulla oblongata and fourth ventricle. The accompanying sketches represent the typical nervous system of an amphibian, -which also resembles that of many fishes, and even the lower Reptilia. The spinal cord (Fig. 374) usually extends through the whole length of t
. Zoology : for students and general readers . Zoology. Mid brain. NEBVOUa SYSTEM OF VERTEBRATES. 393 {Optic lobes, corpora bigemlna or qaadrigemina (tnesen- cepbalon). Crura cerebri. Optic ventricle or Iter a tertio ad quartum ventriculum. Hind brain. Cerebellum (with its ventricle and the pons varolii, form- ing the metencephalon). Medulla oblongata and fourth ventricle. The accompanying sketches represent the typical nervous system of an amphibian, -which also resembles that of many fishes, and even the lower Reptilia. The spinal cord (Fig. 374) usually extends through the whole length of the spinal canal, except in the toads and frogs, birds and many mammals, where it stops short of the end of its canal. In those Vertebrates with limbs, the cord enlarges where the nerves which supply them are sent off ; these are the cervical or thoracic, and lumbar enlargements, especially large in turtles and birds. The white and gray substance of the brain continues in the cord. As the most essential characteristic of Vertebrates is the internal skeleton (endoskeleton) we will enter more into detail in describing it, and afterwards notice the external skeleton (exo- olrolo+nTl^ ^'g- 313—Brain and spinal In the embryosof higher Vertebrates t°™y1iberrcTreb'r°ai and in the adult lancelet, hag-fish and hemispheres; c, optic lobes -, ' c) (i^ cerebellum in the form of a lamprey, the vertebral column is rep- lameiia bridging over the J -. Ti'1 •/ /77 fourth ventncle (.?) ; m, spinal resented by a rod-like axis (notoc/iora cord; t, terminal cord.—After or chorda dorsalis) which is composed '^^"^ ^^^' of indifferent, or only partly organized cells, the substance of the chord resembling cartilage. These chordal cells secrete a membrane called the chordal sheath. The notochord is not. 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 perfect
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
