A text-book of embryology for students of medicine / by John Clement Heisler. With 190 illustrations, 26 of them in colors.

  • Heisler, John C. (John Clement), 1862-1938.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of embryology for students of medicine / by John Clement Heisler. With 190 illustrations, 26 of them in colors. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    though as yet crudely, the external nose, and the upper lip as well. The definite formation of the external nose may be said to be indicated about the eighth week. The orifices of the nasal pits are now the anterior nares, while the pits them- selves have become short canals, opening by their deep orifices, the posterior nares, into the primitive mouth-cavity above the palatal shelves. The nares are separated from each other by the still broad nasofrontal process. That portion of the nasofrontal process that separates the nares gradually becomes thinner and produces the septum of the nose, while its external or superficial part gives rise to the bridge and tip of the organ. The growth of the palate-shelves (Fig. 156) toward the median line, resulting in their union with each other and Fig. 156.—Roof of the oral cavity of a human embryo with the fundaments of the palatal processes (after His), X 10. with the recently-formed septum, definitely divides the nasal chambers from the cavity of the mouth, the posterior nares now opening into the pharynx. This separation is completed toward the end of the third month. The complexity of the adult nasal cavities is produced by the formation of ridges and pouches on the lateral walls of the original nasal pits. Three inwardly projecting horizontal folds of the ectodermic lining of the cavity, the superior, mid- dle, and inferior turbinal folds, ap])ear upon the outer wall of each nasal fossa (Fig. 157). Each fold contains a stratum