THE MAMMALIAN NERVOUS SYSTEM 87 



LIST OF CONDUCTION PATHWAYS 



A. ASCENDING (SENSORY) SYSTEMS 



/. General Somatic Sensory, Exteroceptive 



1. Touch and pressure of trunk and limbs. 



1) Peripheral neurons in spinal nerves. 



2) Secondary path in spinal lemniscus (tr. spino-thalamicus ventralis). 



3) Tertiary path to cortex (projection tract). 



2. Pain and temperature of trunk and limbs. 



1) Peripheral neurons in spinal nerves. 



2) Secondary path in spinal lemniscus (tr. spino-thalamicus lateralis). 



3) Tertiary path to cortex (projection tract). 



3. Cutaneous sensibility of head. 



1) Peripheral neurons in V, IX, and X cranial nerves. 



2) Secondary path in trigeminal lemniscus. 



3) Tertiary path to cortex (projection tract). 



II. General Somatic Sensory, Proprioceptive 

 1. Muscle sense, etc., of trunk and limbs. 



1) Peripheral neurons in spinal nerves and dorsal funiculi. 



2) Thalamic secondary path in medial lemniscus. 



3) Tertiary path to cortex (projection tract). 



4) Cerebellar secondary path in dorsal spino-cerebellar tract. 



5) Cerebellar secondary path in ventral spino-cerebellar tract. 



6) Olivary secondary path in spino-olivary tract (?) . 



III. Special Somatic Sensory, Proprioceptive 

 1. Vestibular nerve. 



1) Peripheral neurons. 



2) Secondary path to cerebellum by vestibulo-cerebellar tract. 



3) Secondary path to cord by vestibulo-spinal tract. 



4) Secondary path to oculomotor and spinal nuclei by fasciculus 



longitudinalis medialis. 



5) Secondary paths to motor nuclei of bulb by arcuate fibers. 



IV. Special Somatic Sensory, Exteroceptive 



1. Cochlear nerve. 



1) Peripheral neurons. 



2) Secondary path from dorsal nucleus, acoustic striae and lateral 



lemniscus. 



3) Secondary path from ventral nucleus, trapezoid body, and lateral 



lemniscus. 



4) Secondary paths to motor nuclei of bulb and midbrain. 



5) Inferior colliculus to thalamus. 



6) Thalamus to cortex (auditory projection tract). 



2. Optic system. 



1) Receptors (rods and cones). 



2) Granule cells of the retina. 



3) "Ganglion" cells of retina. 



a) to colliculus superior. 



b) to thalamus. 



4) Reflex path colliculus superior to cord (tecto-spinal tract) . 



5) Thalamus to cortex (optic projection tract). 



