144 HUMAN PHYSIOLOGY 



General Distribution. 



A. SOMATIC FIBRES. 



(a) Outgoing Fibres. The course of these must be studied 

 in the dissecting-room. 



(6) Ingoing Fibres Cutaneous Fibres. The fibres pass- 

 ing in by each pair of nerves come from zones of skin 

 encircling the body. These are, however, interrupted by the 

 limbs. Each limb may be considered to be an outgrowth at 

 right angles to the trunk, composed of a pre-axial and post- 

 axial part. 



B. SPLANCHNIC FIBRES. 



These are small medullated fibres. 



(a) The Outgoing Fibres may be subdivided as follows 

 (Fig. 76):- 



1. Head and Neck. These leave the spinal cord by the 

 upper five dorsal nerves and pass upwards in the sympathetic 

 cord of the neck to the superior cervical ganglion where they 

 have their cell stations. From these, fibres are distributed 

 to the parts supplied. The chief functions of these fibres 

 are 1st, Vaso-constrictor to the vessels of the face and head ; 

 2nd, Pupilo-dilator (see p. 103) ; 3rd, Motor to the muscle of 

 Miiller; 4th, Secretory to the salivary glands, lachrymal 

 gland, and sweat glands. The course of these fibres is of 

 importance in medicine, since tumours in the upper part of 

 the thorax may press upon them. 



2. Thorax. The fibres to the thoracic organs also come 

 off in the five upper dorsal nerves, have their cell stations in 

 the stellate ganglion, and pass to the heart and lungs. 



3. Abdomen. These fibres come off by the lower six dorsal 

 and upper three lumbar nerves. They course through the 

 lateral ganglia and form synapses in the collateral ganglia of 

 the abdomen the solar plexus and the superior and inferior 

 mesenteric ganglia. From these they are distributed to the 

 abdominal organs, being vaso-constrictor to the vessels, in- 

 hibitory to the muscles of the stomach and intestine, and 

 possibly secretory to the pancreas. 



4. Pelvis. The fibres for the pelvis leave the cord by the 



