File:The pedigree of man - and other essays (1903) (14764443442).jpg

Identifier: pedigreeofmanoth00haec (find matches)
Title: The pedigree of man : and other essays
Year: 1903 (1900s)
Authors: Haeckel, Ernst Heinrich Philipp August, 1834-1919
Subjects: Man Evolution Man Evolution
Publisher: London : A and H.B. Bonner
Contributing Library: ASC - York University Libraries
Digitizing Sponsor: York University - University of Toronto Libraries

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the tongue.They also are very delicate slender cells placed verticallyin the epithelial surface, having their inner ends indirect connexion with very fine terminal fibrils of theolfactory nerve (Figs. 65, 66). As a rule, in the nasalmucous membrane of Vertebrata two kinds of olfactorycells are distinguishable, that in all probability havedifferent offices in respect to the perception of odors.The more slendrer ones, often filiform acicular cells,are markedly swollen in the middle, where the nucleuslies (Fig. 65 e), and carry in the Amphibia a tuft ofexceedingly fine and thin olfactory cilia at their freeends. The broader, rod-like, or cylindrical olfactorycells on the other hand (Fig. 65, a, b) carry no such 320 SENSE ORGANS. cilia, and are regarded by many as simple epithelialcells. The nasal mucous membrane, in which thesecells are placed, lines in the higher Vertebrata, as inMan, the internal wall of the nasal cavity. But it alsois originally a part of the external integument. For
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Fig. 65. Fig. 66. Three olfactory cells from the nose of an Amphibian (Pro-teas). In the middle a larger cylindrical cell (a, withoutcilia ; on each side of it a filiform olfactory cell, swollen inthe middle into a globular shape, and bearing a tuft of verydelicate olfactory cilia at the free extremity. Five olfactory cells from Man, three more delicate, rod-like,and between these, two broader, cylindrical; all are con-nected below with terminal fibrils of the olfactory nerve. the nose begins, even in these higher animals,- in thesame fashion that is persistent in Pisces, their livesthrough, as a pair of depressions of the integument. SENSE ORGANS. 321 Only in the course of embryological development theseolfactory pits (Figs. 52—53 ri) gradually retreat into theinterior of the body, and in like manner in the courseof evolution they have undergone the same change ofplace. The olfactory cells of the nose are, like thegustatory of the tongue, historical derivatives of thegeneral tactil

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