CHAPTEK V 



SPINAL CORD AND NERVES 



CONTENTS. 1. Grey and white matter of the spinal cord. 2. Extra- and intra- 

 spinal nerve-cells ; their connections with the root-fibres and tracts which make 

 up the spinal columns. 3. Spinal roots. Bell-Magendie law of localisation of 

 sensory and motor tracts. Waller's law of degeneration after section. 4. Func- 

 tional relations between afferent and efferent roots. 5. Segmental arrange- 

 ment of spinal roots. 6. Reflex activity of segments of cord ; shock after section 

 of cord. 7. Short and long spinal reflexes; laws of reflex spread. 8. Genesis of 

 spinal reflexes ; central factors that inhibit or promote them. 9. Tonic and 

 automatic functions of spinal cord ; " knee-jerk " or patellar reflex. 10. Trophic 

 functions of spinal cord. 11. Sensory functions and Pfliiger's "spinal soul." 

 12. Spinal cord an instrument of the brain ; spino-cerebral and cerebro-spinal 

 paths of conduction. 13. Localisation of principal spinal centres ; phenomena of 

 spinal deficiency (dogs with amputated cord, Goltz). Bibliography. 



BICHAT distinguished two main parts of the nervous system, 

 the Cerebrospinal System and the Splanchnic or Sympathetic 

 System. The first regulates the relations between the organ- 

 ism and the external world and presides over the functions 

 of animal life; the second controls the relations between the 

 respective organs, and presides over the functions of vegetative 

 (or visceral) life. Acceptable as this dualistic conception of 

 the nervous system may be in the abstract, it should be clearly 

 recognised that it goes too far, and gives rise to error in the 

 localisation and definition of the boundaries between the two parts 

 of the system. The cerebrospinal axis is not completely detached 

 from the sympathetic system. While the two are quite distinct 

 at the periphery to which both are distributed, they intermix in 

 the central nervous system and fuse into a single system. The 

 cerebrospinal axis controls the functions of animal life, but is not 

 thereby excluded from the control of the visceral organs also ; on 

 the other hand, the sympathetic does not represent the entire 

 nervous system of visceral life, but only that part of it which lies 

 outside the cerebrospinal axis. It may thus be treated as the 

 part of the latter which is distributed in the form of gangliated 

 plexuses to the visceral organs. Experimental analysis shows 

 fundamentally the same nervous mechanisms in the ganglia of the 

 sympathetic as exist in the spinal cord. 



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