Title: Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus
Identifier: comparativeembry00nels (find matches)
Year: 1953 (1950s)
Authors: Nelsen, Olin E. (Olin Everett), b. 1898
Subjects: Vertebrates -- Embryology; Comparative embryology
Publisher: New York, Blakiston
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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612 THE DIGESTIVE SYSTEM EPIDERMAL DENTAL LEDGE
Text Appearing After Image:
LABIAL PAPILLAE Fig. 287. Tooth development and arrangement in various vertebrates. (A-D) Tooth relationships with the jaw. (Redrawn and modified from Rand, 1950, The Chordates, Blakiston, Phila. After Wilder.) (E) Dental ledge and developing teeth in the dog shark, Acanthias. (Redrawn and modified from Rand, 1950, The Chordates, Blakiston, Phila. After Kingsley.) (F) Section of the shark's lower jaw indicating a continuous replace- ment of teeth, i.e., a polyphyodont condition. (Redrawn and modified from Rand, 1950, The Chordates, Blakiston, Phila.) (G) Incisor tooth of rodent. (Redrawn and modified from Rand, 1950, The Chordates, Blakiston, Phila. After Zittel.) (H) Horny teeth of 12 mm. frog tadpole. (I) Rudimentary dental lamina in upper jaw of chick. (Redrawn from Lillie, 1930, The Development of the Chick, Holt & Co., N. Y.) (J) Anterior portion of upper jaw of 18-day chick showing egg tooth. the mesenchyme surrounding the developing tooth. Around the base, sides, and crown of the tooth, this mesenchyme condenses and forms the outer and inner layers of the dental sac (fig. 286C). The latter is a connective-tissue sac which surrounds the entire tooth, continuing around the outside of the outer enamel cells of the enamel organ. As the dentine and enamel are de-

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