. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 690 Biology of the Vertebrates 2. Spinocerebellar System Dorsal spinocerebellar tract Ventral spinocerebellar tract 3. Spinothalamic System Lateral spinothalamic tract Ventral spinothalamic tract II. Descending (Motor) Tracts Fasciculus corticospinalis lateralis (Crossed pyramidal tract) Fasciculus corticospinalis ventralis (Direct pyramidal tract) III. Association Tracts Fasciculus proprius dorsalis (Dorsal ground bundle) Fasciculus proprius lateralis (La
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 690 Biology of the Vertebrates 2. Spinocerebellar System Dorsal spinocerebellar tract Ventral spinocerebellar tract 3. Spinothalamic System Lateral spinothalamic tract Ventral spinothalamic tract II. Descending (Motor) Tracts Fasciculus corticospinalis lateralis (Crossed pyramidal tract) Fasciculus corticospinalis ventralis (Direct pyramidal tract) III. Association Tracts Fasciculus proprius dorsalis (Dorsal ground bundle) Fasciculus proprius lateralis (Lateral ground bundle) Fasciculus proprius ventralis (Ventral ground bundle) (a) Ascending Sensory Tracts.âThe fibers which give rise to the so- called dorsal columns are neurites coming from cell bodies located in the dorsal ganglia of the spinal nerves, outside of the cord. As they come into the cord by way of the dorsal root of the spinal nerve, they branch and go both anteriorly and posteriorly, with the longer branch toward the head, and the shorter branch away from the head. Both the longer ascending craniad fibers and the shorter descending caudad fibers send off collaterals that enter the gray matter, where they form synapses with either intermediate neurons or motor neurons. Many of the cranially directed fibers reach without relay as far as the brain itself. Dorsal Root f °f I Spinal Nerve *â. Dorsal SpinocerebellarTract"7 v/' \ Dorsal Horn of Gray Matter *\a / Ventral Horn of Gray Matter ""v~~' Motor Neuron of Ventral Root- Ventral ,' /f"-/~ Spinocerebellar Tract S .vv/Lateral Spinothalamic Tract "âVentral Spinothalamic Tract Fig. 618. The various central connections, within the cord, of sensory neurons. (After Ranson.) Thus a neurite entering the cord through a dorsal root makes numerous central connections many of which are through its large number of collat- erals (Fig. 618). Some collaterals terminate in the ventral gray matter. Pleas
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