CONTENTS xxix 



BOOK III. 



THE CENTRAL NERVOUS SYSTEM AND ITS INSTRUMENTS. 



CHAPTER I. 

 The Spinal Cord. 



SECTION I. 

 On some Features of the Spinal Nerves. 



PAGE 



§ 448. The spinal nerves 675 



§ 449. On efferent and afferent impulses 676 



§ 450. Efferent fibres run in the anterior root and afferent fibres in the 



posterior root 677 



§ 451. The " trophic " influence of the ganglion of the posterior root ; the 



degeneration of nerve fibres 678 



SECTION II. 

 The Structure of the Spinal Cord. 



§ 452. The general features of the cord ; grey and white matter. The 

 grouping of the nerve cells. The cells of the anterior and pos- 

 terior horn, the lateral group, Clarke's column, and the lateral 

 horn. The tracts of white matter. Median posterior column, 

 external posterior column. The evidence of the differentiation 

 of the white matter into tracts. Ascending and descending 

 degeneration. Descending tracts : crossed and direct pyramidal 

 tracts, antero-lateral descending tract. Ascending tracts : cere- 

 bellar tract, antero-lateral ascending tract, median posterior 

 tract 681 



§ 453. The special features of the several regions of the spinal cord. The 

 conus medullaris, the lumbar, and cervical swellings. Varia- 

 tions in the sectional area of the white matter .... 689 



§ 454. Variations in the sectional area of the grey matter .... 691 



§ 455. The relative size, form, and features of transverse sections of the 



cord at different levels 692 



§ 456. Variations in the several columns of white matter at different levels 693 



SECTION III. 

 The Reflex Actions of the Cord. 



§ 457. The difficulties attending the experimental investigation of the cen- 

 tral nervous system ; ' shock ' and other effects of an operation 696 



§ 458. The differences, as regards reflex movements, between different 

 kinds of animals. The features of a reflex act dependent on the 

 character of the afferent impulses 698 



