SYMPATHETIC GANGLIA 



497 



viscera. Whatever may turn out to be the function of 

 the sympathetic ganglia, there is at present no adequate 

 evidence that they in any way act as nervous centres, 

 either of reflex action, or of any other form of nervous 

 activity. Hence the sympathetic is not to be regarded as 

 a separate nervous system, but as being in reality merely 

 an outlying part of the cerebro-spiual system, an outlying 

 chain of ganglia, through which the fibres of a part of 

 the trunk of each spinal nerve pass on their way to the 

 viscera. This relationship is made quite clear by the 

 accompanying diagram (Fig. 157). 



We have spoken of the fibres which proceed from cells 



Fio. 158. — Pale Non-medullated Fibres from the Pneumooastric 

 Nerve. (Ranvier.) 



n, nucleus ; p, protoplasm belonging to the nucleus. 



situated in the sympathetic system as non-medullated, 

 because they possess no medulla. They appear under the 

 microscope as pale flattened bands, about as wide as 

 small meduUated fibres, often fibrillated longitudinally, 

 and frequently dividing. They appear, in fact, to be 

 axis-cylinders, without medulla, and in cases perhaps 

 without a neurilemma, though they bear at intervals 

 on their surface nuclei which may represent the inter- 

 nodal nuclei of ordinary nerve fibres. 



The ganglia of the sympathetic system are composed of 

 nerve cells bound together by a small amount of loose 

 connective tissue. The cells diff"er somewhat in ap- 

 pearance and arrangement according to the ganglion in 



K K 



