Section 8. 

 The Sympathetic or Autonomic System of Nerves. 



It will have been observed in connection with the cerebro- 

 spinal system of nerves that the bulk of the functions dealt with 

 had reference to the movements of the body and the question of 

 sensation. Excluding entirely the nerves of special sense and 

 the faculties, and speaking generally, the cerebro-spinal system 

 deals with the movement of skeletal muscles and the cutaneous 

 and muscular sensations. It does not touch on the question of 

 the secretion of glands, the movements of the heart and blood- 

 vessels, the movements of the intestines and pelvic viscera, the 

 movements of the body hairs, or the movements of the pupil. 

 It is true that at p. 472 centres were described as existing in the 

 cord regulating some of these functions, but it was made clear 

 at the time that their operations were carried out through the 

 sympathetic system. 



The sympathetic system lies outside the cerebro-spinal axis, 

 and if it could be dissected out intact it would be found to con- 

 sist of a long cord extending from the root of the neck to the 

 sacrum, and studded with nodules, which are the ganglia. 

 This cord is connected in the abdominal region with larger masses 

 of nerve-tissue, also ganglia, which in turn are linked up with 

 microscopic ganglia in far-off tissues. Dissection would show also 

 that it was not possible to remove the system from the body 

 without dividing a series of nerves passing out from the spinal 

 cord, and to which it is attached. Here, then, we have a bird's- 

 eye view of the sympathetic system as a network of fibres and 

 ganglia laid down on definite lines, though irregularly disposed, 

 placed outside the cerebro-spinal axis, yet in direct communica- 

 tion with the spinal cord. 



Bearing this arrangement in mind, it is not surprising that 

 the sympathetic is regarded as a distinct nervous system ; it 

 is certainly distinct as regards its function, and it is peculiar 

 in the arrangement of structure ; yet there is nothing from a 

 structural point of view which does not already exist in the 

 spinal system. It is dependent on the cerebro-spinal system for 

 the fibres with which it works, but, having obtained them, it 

 elaborates them into a system peculiar to its own needs, and 

 through its ganglia is enabled, for some of the functions it carries 

 out, to be for the time being independent of the spinal cord. 

 We know, for instance, that the intestines will continue to move 

 when all spinal connections are severed. 



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