628 HANDBOOK OF PHYSIOLOGY. 



(a) i. Vaso-motor or Vaso-constrictor and Cardio-augmentor F, bres. 

 The vaso-motor nerves for all parts of the body come from the central 

 nervous system, and pass out from the spinal cord in the white rami vis- 

 cerales of the thoracic region from the 2d thoracic to the 2d lumbar 

 nerve roots inclusive, as fine medullated fibres; they then pass to the 

 lateral or main sympathetic chain, become non-medullated, and are dis- 

 tributed to their muscles either directly or through terminal ganglia. 

 Thus the augmentor nerves of the heart arise in the thoracic rami, pass 

 upwards, and are distributed to the heart through the ganglion stellatum 

 or inferior cervical ganglion; the vaso-motor nerves for the arm pass out 

 of the cord below the origin of the roots of the brachial plexus, in the 

 anterior roots of the 2d and lower thoracic nerves, and reach that plexus 

 by the same ganglion; the vaso-motor nerves of the foot leave the spinal 

 cord high up, and reach the sympathetic lateral ganglia above the origin 

 of the sciatic nerve, into which they pass through the abdominal sympa- 

 thetic. In all cases the nerves lose their medulla in the ganglia. Simi- 

 larly the vaso-motor nerve supply for the blood-vessels of the head and 

 neck and of the abdomen is derived from the cervical and abdominal 

 splanchnics respectively, or from the corresponding rami efferentes of 

 the upper lumbar ganglia. 



The lateral sympathetic chain G-askell proposes to call the chain of 

 vaso-motor ganglia. 



ii. Vaso-inhibitory or Vaso-dilator, and Cardio-inhibitory Fibres. 

 Of these, which are doubtless as widely distributed as the vaso-motor 

 fibres, we have distinct proof in the existence of fibres separate from vaso- 

 motor, e. g., in the inhibitory nerve of the heart, the cardio-vagus; in 

 the chorda tympani; in the small petrosal, and in the nervi erigentes. 



These nerve-fibres, as far as we know at present, leave the central 

 nervous system among the fine medullated nerves of the cervico-cra- 

 nial and sacral rami communicantes, do not enter the lateral ganglia, 

 but pass without losing their medulla into the collateral or terminal gan- 

 glia. 



(b.) i. Viscera-motor Fibres. These fibres, upon which depend the 

 peristaltic movements of the thoracic portion of the oesophagus, and of 

 the stomach, and intestines, arise from the central nervous system, as 

 the fine medullated fibres of the upper portion of the cervical region, not 

 in the spinal nerve roots of that region, but as the bundles of fibres 

 which may be called the rami viscerales of the vagus and accessory nerves. 

 They pass to the ganglion of the trunk of the vagus, where they lose 

 their medulla. 



ii. Viscero-Inhibitory Fibres. It appears that the nerve- supply to 

 the circular muscles of the alimentary canal and its appendages is con- 

 tained in the abdominal splanchnics, and consists of those fibres which 



