1020 



THE NERVOUS SYSTEM 



which convey twigs of the third and fourth cervical nerves (fig. 774). The lateral part of the 

 neck receives filaments from the second, third, and fourth cervical nerves by way of the great 

 auricular, small occipital, and middle supraclavicular (supra-clavicular) branches of the cervical 

 plexus, and posteriorly the skin of the neck is supplied by the small occipital nerve and by the 

 medial branches of the posterior primary divisions of the cervical nerves from the second to 

 the sixth inclusive (fig. 776). 



The Cutaneous Areas of the Trunk 



The skin over the ventral aspect of the trunk as far down as the third rib is supplied by 

 the anterior supra-clavicular (suprasternal) and middle supra-clavicular (supra-clavicular) 

 branches of the cervical plexus, which contain filaments from the third and fourth cervical 

 nerves (fig. 776). From the third rib to the lower part of the abdominal wall the skin receives 

 the anterior cutaneous branches, and the anterior divisions of the lateral cutaneous branches of 



Fig. 



775. — Diagram of the Cutaneous Areas op the Side of the Body and Part of the 



Limb. (After Head.) 



the thoracic nerves except the first, second, and twelfth (fig. 776). The skin over the lower 

 and anterior part of the abdominal wall is supplied by the ilio-hypogastric branch of the first 

 lumbar nerve. 



The cutaneous supply of the lateral aspects of the body is derived from the lateral branches 

 of the anterior primary divisions of the thoracic nerves from the second to the eleventh, and 

 the skin over the dorsal aspect of the body is supplied laterally by the posterior divisions of 

 the lateral branches of the thoracic nerves from the third to the eleventh, and medially by the 

 posterior primary divisions of the thoracic nerves, in the upper half by their medial branches 

 and in the lower half principally by their lateral branches. 



THE CUTANEOUS AREAS OF THE LIMBS 



The areas of skin of the upper and lower limbs which are supplied by the branches of the 

 brachial, jiinibar, and sacral phixiisos are indicated in fig. 776, and the spinal nerves which con- 

 tribute toe.'icii iKTve area an; noted. Tlie (luci.stion of the skin areas supi)lied l)y;iny given spinal 

 nerve is one; of great clinical importance, in conncf^tion with the diagnosis of injuries of nerves 

 and of pathological conditions aiTecting them, 'i'lierefore, considerable attention has been 

 directed to the matter and it has been found that the areas which become hypersensitive 

 when certain spinal nerve-roots are irritated, or ana3sthetic when the roots are destroyed, do 



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