344 CEREBRO-SPINAL NERVES. 



and lateral branch of the last dorsal nerves ; internally by the posterior divisions of 

 the sacral nerves ; externally by the posterior branch of the external cutaneous 

 nerve (2, 3 7) proceeding from the front ; and inferiorly by the perforating 

 cutaneous nerve (2, 3 s) and branches of the small sciatic nerve (1, 2, 3 s) proceeding 

 from below. 



The thigh is supplied externally by the external cutaneous nerve (2, 3 7) from the 

 lumbar plexus ; posteriorly, and in the upper half of its inner aspect, by the small 

 sciatic (1, 2, 3 s) ; anteriorly, and in the lower half of the inner aspect, by the middle 

 and internal cutaneous (2, 3 7) of the anterior crural, the latter being frequently 

 assisted by the obturator nerve (2, 3, 4 I). 



The leg is supplied posteriorly by the small sciatic (1, 2, 3 s) and short saphenous 

 (1, 2 s) nerves; internally by the long saphenous (3, 4 /) and branches of the 

 internal cutaneous of the thigh (2, 3 7) (or obturator) ; and outside and in front by 

 cutaneous branches of the external popliteal nerve (5 7, 1, 2 s) and by its musculo- 

 cutaneous branch (4, 5 7, 1 s). 



On the dorsum of the foot are the branches of the musculo -cutaneous (4, 5 7, 1 s), 

 supplying all the toes with the exception of the adjacent sides of the first and second, 

 which are supplied by the anterior tibial (4, 5 7, 1 s), and the outer side of the little 

 toe, which, with the outer margin of the foot, is supplied by the short saphenous 

 nerve (1, 2 s). The long saphenous (3, 4 7) is the cutaneous nerve of the inner side 

 of the foot. 



The sole of the foot is supplied in its posterior part, together with the inner side 

 of the heel, by the calcaneo-plantar branch of the posterior tibial nerve (1, 2 s). 

 In front of this, the inner and larger part is supplied by the internal plantar 

 nerve (4, 5 7, 1 s), which extends ^to the inner three toes and a half, while the outer 

 part, with the remaining one toe and a half, is supplied by the external plantar 

 nerve (1, 2 s). Over the outer side of the heel, and along the outer margin of the 

 sole, are branches of the external saphenous nerve (1, 2 s). 



CUTANEOUS DISTRIBUTION OF THE SPINAL NERVES TO THE TRUNK 



AND LIMBS. 



The manner in which the several spinal nerves are distributed to the skin has 

 been greatly elucidated by the experimental investigations of Sherrington, the 

 dissections of Herringham and Paterson, and the clinical and pathological 

 observations of Koss, Thorburn, Head, and others. From these it would appear 

 that in the trunk the branches of each dorsal (segmental) nerve are generally 

 distributed to a continuous area of skin, which has the form of a zone extending 

 horizontally or obliquely from the dorsal to the ventral median line (see fig. 225, 

 A, B, C). According to the observations of Head, the upper dorsal nerves 

 form exceptions to this statement, their zones being interrupted laterally by the 

 interposition of the upper limb, into which the middle portions of the first and 

 second nerves (corresponding to their lateral cutaneous offsets) are prolonged ; but 

 Sherrington found in the monkey that there was complete continuity between the 

 trunk and limb portions of the areas of these nerves. Inferiorly, the zone of the last 

 dorsal nerve is produced downwards over the hip ; and the first lumbar nerve, which 

 resembles a dorsal nerve in its distribution, also supplies a zone which is similarly 

 extended laterally over the hip, as well as ventrally to the penis, scrotum, and upper 

 part of the thigh ; while with the second lumbar nerve the series of limb-nerves 

 proper commences. These zones, moreover, overlap to a considerable extent, owing 

 partly to the communications established between the several trunks, as is especially 

 the case with the lower intercostal nerves (see p. 310), and partly to the crossing of 



