Diseases of the nervous system / edited by Archibald Church.

Date:
1908
Catalogue details

Licence: In copyright

Credit: Diseases of the nervous system / edited by Archibald Church. Source: Wellcome Collection.

    125/1256 page 97
    The fibers of the lateral root pass on posteriorly into the temporal lobes. Later we will again follow them. In regard to the secondary optic tract, we must assume that the external geniculate body, the anterior corpora quadrigemina, and the pulvinar of the thalamus neurons of the second division develop from the three terminal stages of the optic tract, like those in the lemniscus. The fibrillations of the first terminal stages of this nerve, so far as we know at present, pass directly to the cortex of the brain without ending in nuclei extending toward the cauda like the fibers of the lemniscus. There- fore this higher optic tract does not correspond to the second, included within the temporal tract, but to that third sensory neuron which is now to be de- scribed. (3) THE THIRD SENSORY NEURONS The complicated mechanism of the sensory conduction tract compared with the motor, which is evident from this description, is explained by the fact that in man as well as in all vertebrate animals there is a third sensory neuron in addition to the two neurons we have discussed. The marked devel- Stratum zonale Lemniscus lateralis colliculi inferiores Basis pedunculi Recessus pos- terior fossae interpeduncu- laris (Tarini) Lemniscus tract to the basis pedunculii Fibrae pontis su- perficiales Sulcus lateralis mesencephali Lemniscus medialis Substantia nigra Stratum griseum centrale Aquaeductus cerebri (Sylvii) Nucleus n. troch- learis Radix descendens (mesencephalica) n. trigemini Nucleus lemnisci — lateralis Fasciculus lon- gitudinalis medialis Decussatio brachii con- junctivii Fig. 97.—Transverse Section through the Upper Margin of the Pons and the Poste- rior Corpora Quadrigemina. (After Toldt.) opment of the anterior brain (cerebrum) in the primates, the higher stage of conscious sensation, are probably intimately related to this. It is scarcely necessary to state that collaterals in an unentwined web pass to other centers of other neuron groups with unknown functions, especially in the cortex of the brain itself, and are combined in various ways with others in the sensory tract.
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