Manual of pathology : including bacteriology, the technic of postmortems, and methods of pathologic research . uppercranial bones develop inthe situation where thegroove fails to close. Inthese cases malformationsof the brain or cord result,the character of which de-pends on the situation,kind, and extent of theareas of the groove notclosed over. We possessno accurate informationas to the cause of theseconditions; the general aspects of teratogenesis are discussed on page Totalis, i—When the entire medullary grooveremains patent, neither the skull nor the vertebrae clos
Manual of pathology : including bacteriology, the technic of postmortems, and methods of pathologic research . uppercranial bones develop inthe situation where thegroove fails to close. Inthese cases malformationsof the brain or cord result,the character of which de-pends on the situation,kind, and extent of theareas of the groove notclosed over. We possessno accurate informationas to the cause of theseconditions; the general aspects of teratogenesis are discussed on page Totalis, i—When the entire medullary grooveremains patent, neither the skull nor the vertebrae close posteriorly;the resulting condition is called craniorrhachischisis totahs. A fetus thatat birth presents this malformation is found to possess, on the dorsal sur-face of its trunk, a wide, shallow depression, uncovered by skin, occupyingthe median line, which, passing upward, becomes expanded over theposterior part of the head. In the median Hne of this fissure, flattened> Given, Proceed. Path. Soc. of Phila., June, 1902. n. s., vol. v, p. 266. Vur-pas and Leri, C. R. Acad, des Sci., July 20. Fig. 405.—Ckani(irkha( HisrHisis Totalis. There is a small amount of brain substance present and a few shred;^ of nervous tissue in the spinal grove. THE NERVOUS SYSTEM. S43 out over the bodies of the vertebnc. are found varying amounts of adehcate, soft, and very vascular tissue, consisting of the rudimentsof the brain and cord; in rare instances no nervcnis tissue can be dem-onstrated. In many cases, however, the anterior part of the brain isfairly well developed. The external surface of the fissure is covered bycolumnar epithelium, which is continuous on each side with the sr|ua-mous epithelium of the skin, and corresponds to the epithelial lining of thecentral canal of the cord and the ventricles of the brain. Between therudimentarv nerve substance and the bodies of the vertebra arc thehighlv vascular tissues of the pia and arachnoid, and, still more deeply, afibrous me
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