127 



nerves and vertebrae not only in animals of different species but also 

 in the individuals of a given species. This variation is more marked 

 in the lumbo-sacral than in the brachial plexus. It has been found 

 in every species of animal in which it has been looked for. To 

 EiSLER we are indebted for the most extensive study yet made of 

 the variations in the lumbo-sacral plexus of man. A summary of the 

 literature bearing upon the subject will be found in his paper referred 

 to above and in Wichmann's valuable book "Die Rückenmarksnerven'', 

 Berlin 1900. 



Relation of the Spinal Nerves to the Nerves of the Limb. 



In all vertebrates the nerves of supply are carried into the 

 limbs by large nerve trunks composed of bundles of fibres from 

 several spinal nerves. In man, as in 

 the mammals in general, the main 

 nerves of the posterior limb are four 

 in number, the obturator, femoral, tibial 

 and peroneal nerves (see Fig. 1). 



Of these, the obturator and femoral 

 nerves arise from the lumbar plexus, 

 usually by separate roots from the 

 (XXI) XXII, XXIII and XXIV spinal 

 [(1.) 2., 3. and 4. lumbar] nerves. They, 

 together with their branches, serve to 

 supply the musculature and skin of 

 the anterior aspect of the limb. In a 

 general way the femoral nerve supplies 

 the an tero- lateral, the obturator, the 

 antero-median aspect of the limb. 



The lateral (external) cutaneous 

 nerve belongs with the femoral nerve, 

 being more or less closely bound up 

 with its trunk or with its roots of 



pudic N, 



Fig. 1. Diagram to show the relation of 

 the main nerves of the limb to the skeleton. In 

 order that the main general relations may be 

 made clear some of the nerves are represented 

 slightly out of their true positions. For instance 

 the femoral nerve is shown drawn too far towards 

 the femiir. 



XXI spinal N. 



iliohypogastric N 



inguinal N. 



- XXIV spinal N. 



liUeral cut K 



XXN'III spinnl N. 

 s gluteal N. 



V femoral N. 



^peroneal 2^ 



deep peroneal N. 



Bapbeoous K 



sup. peroneal N. 



mt plantar X 



origin. The territory of the femoral nerve includes the iliopsoas, 

 pectineus, and sartorius muscles, and the extensor muscles 'of the 



