ioo8 



HUMAN ANATOMY. 



intervening nerve-fibres, a small amount of connective tissue prolonged from the 

 endoneurium of the nerve-bundles and accompanying the blood-vessels being also 



Fig. 852. 



Posterior root (sensory ) 



Spinal cord 



Spinkl ganglion 



Posterior 

 division 



V^:"- 



H--- 



Anterior (motor) root 

 Common trunk of spinal nerve 



Anterior division 

 Section of spina! nerve, showing its roots, ganglion, common trunk and primary divisions. X 10. 



Fig. 853. 



Nerve-fibres, .cut transversely 





Nerve-cell 



present. The chief ganglion-cells are from .060-. 080 mm. in diameter, but some 

 measure as much as .170 mm. and others as little as .025 mm. In sections 



(Fig. 853) they usually appear round or oval, 

 since only exceptionally are their processes to 

 be seen. Each cell is enclosed by a richly 

 nucleated capsule which is continuous with the 

 sheath of the nerve-fibres. Most of the many 

 other oval nuclei that are conspicuous in sections 

 of the ganglia belong to the neurilemma of the 

 ner^•e-fibres and, hence, are seen as chains ex- 

 tending in different planes. Although many 

 of the nerve-cells within the spinal ganglia are 

 the cell bodies of the sensory neurones, whose 

 processes course as medullated fibres within 

 the spinal nerves, many more are small cells, 

 whose axones never acquire a medullary coat 

 and, dividing into peripheral and central 

 branches, run within the trunks and posterior 

 roots of the nerves as nonmedullated fibres. 

 Based largely on the behavior of their axones, 

 Dogiefi has described eleven types of cells 

 within the ganglia. Ranson regards the "large" and "small" cells, whose axones 

 become medullated and nonmedullated fibres respectively, as an important grouping, 



^ Der Bau der Spinalgangiien, Jena, 1908. Dogiel describes eleven varieties of nerve-cells. 



Capsule 



Nerve fibres 



Section of spinal ganglion, showing nerve-cells 

 surrounded by nucleated capsules. X ?,oo. 



