An American text-book of physiology . , the nerve-cell body stimulated at any point may be responsive just asan amoeba is responsive at any portion of its surface. When, however, thebranches are formed they become the channels through which the impulsespass, and hence assume a special significance without indicating any funda-mental change in the structure of the cell. Where the cell has well-developed 1 Davenport: Bulletin of the 3 of Comparative Zoology, Harvard College, Nov., 1895;Herbst: Biologviche Centralblatt, 1894, Bd. xiv. * Mali: Journal of Morphology, 1893, vol.
An American text-book of physiology . , the nerve-cell body stimulated at any point may be responsive just asan amoeba is responsive at any portion of its surface. When, however, thebranches are formed they become the channels through which the impulsespass, and hence assume a special significance without indicating any funda-mental change in the structure of the cell. Where the cell has well-developed 1 Davenport: Bulletin of the 3 of Comparative Zoology, Harvard College, Nov., 1895;Herbst: Biologviche Centralblatt, 1894, Bd. xiv. * Mali: Journal of Morphology, 1893, vol. viii. » Koster: Neurologische Centralblatt, 1889, Bd. viii. * Archivfiir Anatomie tind Physiologie, 1889. (312 . AMERICAN TEXT-BOOK OF PHYSIOLOGY. brandies we expect an arraii<^enant of thcin such tliat the impulse .shall enterthe cell-body by one branch and leave it by another. On examining tlie mature nerve-cells of man with this idea in mind, twotypes arc found. The first type may be exemplified by tlu! pvraniidal cortical. Fig. 146 —^-Z), showing the pliylogcnetic development of mature nerve-cells in a series of ver-tebrates; a-e, the ontogenetic development of growing cells in a typical mammal; in both cases onlypyramidal cells from the cerebrum are .shown; .1, frog; i;, lizard; ; ; a, neuroblast withoutdendrons; 6, commencing dendrons; c, dendrons further developed; d, first ajjpearance of collateralbranches; e, further development of collaterals and dendrons (from S. Ram6n y Cajal). cells shown in Figure 146. Plere, from a pyramidal body {D) there arise anumber of , while from the lower portion of the cell the neuron growsout and branches. In the other type the neuron alone grows out. Its branches
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