THE AUTONOMIC NERVOUS SYSTEM 525 



region will be erected, the maximum movement of the hairs being near the 

 middle of the strip. This marks the area of distribution of the pilomotor nerves 

 given by the eleventh thoracic nerve to the sympathetic. If then the strength 

 of the shock be increased to a certain point, the hairs in the long strip will of 

 course be erected as before, but in addition there will be energetic erection 

 of hairs in a short strip a little distance above the long strip, and separated 

 from it by a quiescent region. This short strip is the same as that affected 

 by stimulating the grey ramus or the dorsal cutaneous branch of the eleventh 

 thoracic nerve. It marks the area of distribution of the pilomotor fibres received 

 by the spinal nerve from the sympathetic " (Langley). 



We may now indicate briefly the main course and functions of 

 the fibres of the sympathetic system. 



(1) The head and neck are supplied by fibres leaving the spinal 

 cord by the first five dorsal nerves (chiefly by the second and third). 

 They all have their cell station in the superior cervical ganglion. 

 They convey : 



Vaso-constrictor impulses to the blood-vessels. 



Dilator fibres to the pupil. 



Secretory (trophic ?) fibres to the salivary glands and sweat 



glands. 

 Vaso-dilator fibres to the lower lip and pharynx (?). 



(2) The thoracic viscera (heart and lungs) are supplied by the 

 same five nerve-roots. The cell station of these fibres is, however, 

 situated in the stellate ganglion. They convey : 



Accelerator or augmentor impulses to the heart. 



(3) The abdominal viscera receive fibres from the lower six dorsal 

 nerves and the upper three or four lumbar. Most of these fibres 

 run through the sympathetic chain without making any connection 

 with the ganglia, and have their cell stations in the collateral ganglia 

 of the solar plexus, the semilunar and superior mesenteric ganglia. 

 On their way to these ganglia they form the greater and lesser 

 splanchnic nerves. Their functions are : 



Vaso-constrictor for stomach and small intestine, kidney, and 



spleen. 



Probably vaso- dilator for the same viscera. 



Inhibitory for both muscular coats of stomach and small intestine. 

 Motor for ileocolic sphincter. 



(4) The pelvic viscera are supplied by the lower dorsal and upper 

 three or four lumbar nerve-roots. These fibres also pass by the 

 main chain to make connections with the cells chiefly in the inferior 

 mesenteric ganglia. They convey : 



Vaso-constrictor impulses to pelvic viscera. 

 Inhibitory fibres to colon (both coats). 

 Motor and also inhibitory fibres to bladder. 

 Motor fibres to retractor penis. 



