102 ESSENTIALS OF PHYSIOLOGY. 



ineffective, it is clear that they have their cell station in that ganglion. 

 For example, when nicotine has been painted on the superior cervical 

 ganglion, stimulation of the cervical sympathetic nerve produces none 

 of the effects which are observed in the normal animal, whereas 

 stimulation of the fibres leaving the ganglion produces the same effect 

 after the application of nicotine as before. The experiment shows that 

 the fibres running in the cervical sympathetic nerve have their cell 

 stations in the superior cervical ganglion. 



The fibres of the autonomic system supply not only the blood- 

 vessels but other structures, including the walls of the digestive tract 

 and pelvic viscera, the heart, sweat glands, and hairs. Their course 

 and function will be fully considered in subsequent chapters, but may 

 be summarised here. 



I. Cranial autonomic fibres. 



Third nerve. The autonomic fibres pass to the ciliary ganglion, 

 where they have their cell station, and supply the intrinsic muscles 

 of the eye. 



Seventh and ninth nerves. The autonomic fibres supply vaso- 

 dilator fibres to the tongue, and secretory fibres to the salivary glands. 



The vagus sends inhibitory fibres to the heart, motor fibres to the 

 oesophagus, stomach, small intestine, and bronchioles, and secretory 

 fibres to the stomach and pancreas ; the cell stations probably lie in 

 the walls of the structures supplied by the different fibres. 



II. Sacral autonomic fibres. These supply dilator fibres to the 

 blood-vessels of the penis, and motor fibres to the muscles of the 

 rectum and bladder. 



III. Sympathetic fibres. 



(1) The fibres to the head leave the spinal cord in the first five 

 thoracic white rami, and run in the cervical sympathetic nerve ; this 

 contains vaso-constrictor fibres for the blood-vessels, secretory fibres 

 for the salivary glands, and dilator fibres for the pupil. 



(2) The fibres to the heart have their cell station in the stellate 

 ganglia, and convey accelerator impulses. 



(3) The fibres to the abdominal viscera leave the spinal cord in 

 the lower six thoracic and the first lumbar white rami. Most of them 

 have their cell stations in the semi-lunar and superior mesenteric 

 ganglia, from which they are distributed. They convey constrictor 

 impulses to the blood-vessels of the stomach, small intestine, kidneys, 

 and spleen, inhibitory impulses to the muscular walls of the stomach 

 and small intestine, and motor impulses to the ileo-colic sphincter. 



(4) The pelvic viscera are supplied from the white rami of the last 

 thoracic and upper lumbar nerves, the cell station being in the 



