SENSORY DISTRIBUTION. 341 



nerve ; in the rest of its extent it is supplied by the glosso-pharyngeal and pneumo- 

 gastric nerves, mainly through the pharyngeal plexus, but in the neighbourhood of 

 the superior aperture of the larynx it receives filaments of the superior laryngeal 

 nerve. The larynx is supplied mostly by the superior laryngeal nerve, but in its 

 lowest part it receives fibres from the inferior laryngeal, which also supplies 

 the trachea. The sensory nerves of the (fsopliagus are probably derived from 

 the pneumo-gastric. 



The mucous lining of the tympanic cavity and Eustachian tiibe are supplied 

 by the glosso-pharyngeal nerve, while to the mastoid cells filaments pass from the 

 same source, as well as from the inferior maxillary nerve (Luschka). The outer 

 surface of the tympanic membrane, like the skin of the external auditory meatus 

 generally, is supplied by the auriculo-temporal of the fifth and the auricular branch 

 of the pneumo-gastric nerves. 



In the cranial cavity the dura mater receives branches from the three divisions of 

 the fifth, the pneumo-gastric, and the hypoglossal nerves. 



2. In the trunk. The posterior divisions of the spinal nerves supply an area 

 extending on the back from the vertex of the skull to the buttock. This 

 area is narrow in the neck ; it is expanded in the upper dorsal region, extending 

 over the back of the scapula; in the lower dorsal and lumbar regions its extent may 

 be marked by a line drawn from the lower angle of the scapula (the arm hanging 

 against the side) to the middle of the iliac crest ; and in the buttock its lower limit 

 is indicated by a line from the tip of the coccyx to the great trochanter (see fig. 189, 

 p. 282). The series of cutaneous branches is not continuous, there being gaps in 

 the lower cervical and lower lumbar regions, corresponding to the middle parts 

 of the brachial and lumbo-sacral plexuses ; that is, those spinal nerves which 

 contribute most largely to the supply of the limbs do not furnish dorsal cutaneous 

 offsets. 



The area supplied by the cervical plexus, besides extending upwards, as already 

 mentioned, on the lateral part of the skull, stretches over the front and sides 

 of the neck, and the upper part of the shoulder and breast. 



The area of the anterior divisions of the dorsal and first lumbar nerves meets 

 superiorly with that of the cervical plexus, and posteriorly with that of the posterior 

 divisions of the dorsal and lumbar nerves. It passes down over the haunch 

 and along by the outer part of Poupart's ligament, and includes part of the penis 

 and scrotum, and a small portion of the integument of the thigh internal to 

 the saphenous opening. This extensive area may be subdivided by a line passing 

 through the nipple downwards to the centre of Poupart's ligament into a mesial 

 region supplied by the anterior cutaneous branches of the nerves, and a larger 

 lateral region supplied by the lateral cutaneous branches. In the former region the 

 skin over the ensiform process is supplied by the sixth and seventh dorsal nerves, and 

 that around the umbilicus usually by the tenth dorsal nerve. 



The root of the penis on its dorsal aspect and a part of the scrotum anteriorly are 



Fig. 221. CUTANEOUS AREAS OF THE NERVES OP THK UPPER LIMB. (Gr.D.T. ) 

 A, anterior view ; B, posterior view. 



The areas supplied by the circumflex and musculo-spiral nerves, derived from the posterior cord of 

 the brachial plexus, are circumscribed by red outlines ; those of the ulnar, internal cutaneous, and 

 nerve of Wrisberg (W), from the inner cord of the plexus, together with the intercosto-humeral nerve, 

 by blue lines ; and those of the mus3ulo-cutaneous from the outer cord of the plexus, with the median 

 derived from both outer and inner cords, by interrupted black lines. The lower limit of the supra- 

 clavicular nerves over the shoulder is also shown by a broken black line. The numerals following the 

 names of the nerves indicate the spinal nerves from which the latter arise ; 3, 4, 5, 6, 7, 8, the 

 corresponding cervical nerves ; 1, 2, the first and second dorsal nerves. The cutaneous branches of the 

 musculo-spiral are distinguished as follows : I, internal cutaneous ; II, upper, and III, lower 

 external cutaneous. 



