Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30. (Neural fold labeled at center left, third from the bottom.)
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| colspan="2" |
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| colspan="2" |
|- class="hiddenStructure"
|Latin
|colspan="2"|
|- class="hiddenStructure"
|[[List of subjects in Gray's Anatomy:7#Gray.27s_page_.23|Gray's]]
|colspan="2"|[subject #7 ]
|- class="hiddenStructure"
|System
|colspan="2"|
|- class="hiddenStructure"
|Carnegie stage
|colspan="2"|[9]
|- class="hiddenStructure"
|Days
|colspan="2"|
|- class="hiddenStructure"
|Precursor
|colspan="2"|
|- class="hiddenStructure"
|Gives rise to
|colspan="2"|
|- class="hiddenStructure"
|MeSH
|colspan="2"|[]
|- class="hiddenStructure"
|Dorlands/Elsevier
|colspan="2"|[f_11/12371345]
|}
In front of the primitive streak two longitudinal ridges, caused by a folding up of the ectoderm, make their appearance, one on either side of the middle line. These are named the neural folds; they commence some little distance behind the anterior end of the embryonic disk, where they are continuous with each other, and from there gradually extend backward, one on either side of the anterior end of the primitive streak.
