. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 138 COMPARATIVE MORPHOLOGY OF VERTEBRATES. The close association of sensory and motor nerves in the trunk region of verte- brates is not yet satisfactorily explained. The fact that in Amphioxus the two kinds of nerves are independent of each other throughout their course shows that the vertebrate condition is not primitive. The infolding of the nervous plate has been described (p. n) and with that stage the present account begins. As the plate is broad- est in front, the result is a larger anterior portion of t
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 138 COMPARATIVE MORPHOLOGY OF VERTEBRATES. The close association of sensory and motor nerves in the trunk region of verte- brates is not yet satisfactorily explained. The fact that in Amphioxus the two kinds of nerves are independent of each other throughout their course shows that the vertebrate condition is not primitive. The infolding of the nervous plate has been described (p. n) and with that stage the present account begins. As the plate is broad- est in front, the result is a larger anterior portion of the tube, the brain, while the rest of the tube gives rise to the spinal cord. Brain and cord constitute the central nervous system, while the nerves arising from the brain and cord form the peripheral nervous system. CENTRAL NERVOUS SYSTEM. The two halves of the neural plate are separated by a median band of non-nervous tissue, hence, when it is rolled into a tube, the mid- ventral line—the floor plate—is thinner and differs from the side walls. With the closure of the tube (fig. 144, A) a, similar roof plate appears,. 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. Philadelphia, P. Blakiston's son & co.
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