314 



THE SPINAL NERVES. 



the low form of plexus with an additional moveable vertebra, and the high form with assimi- 

 lation of the fifth lumbar vetebra to the sacrum, but this is not always the case. The upper 

 three offsets of the lumbar plexus, not being 1 true limb-nerves, do not vary so much in their 



PUOJ 



Fig. 205. EXTREME FORMS OF LUMBAR AND SACRAL PLEXUSES. (From Eisler.) 



A. High form of plexus : ventral aspect. From a subject in which the fifth lumbar vertebra was 

 assimilated to the sacrum, and articulated on both sides with the ilium. 



B. Low form of plexus : dorsal aspect. From a subject in which there were thirteen dorsal and 

 five lumbar vertebrae. 



origin, although they also are affected at times by the general form of the plexus ; on the 

 other hand, it may happen with a low form of plexus that the ilio-hypogastric and ilio- 

 inguinal nerves receive an additional root from the twelfth dorsal (Paterson) . (J. N. Langley 

 (lumbar plexus of cat), Journ. Phys.. xii. 349, xv. 210. and xvii. 296 ; C. S. Sherrington (cat and 

 monkey), Journ. Phys.. xiii. 639 ; P. Eisler. " Der Plexus lumbosacralis des Menschen," 

 Halle, 1892 ; A. M. Paterson, " The Origin and Distribution of the Nerves to the Lower Limb," 

 Journ. Anat., xxviii, 84). 



Ilio-hypogastric and ilio-iiiguinal nerves. These nerves are the upper 

 two branches of the lumbar plexus. They are both derived mainly from the first 

 lumbar nerve, and have a nearly similar course and distribution, corresponding 

 together to the anterior (intercostal) division of a dorsal nerve. They pass 

 forwards between and through the broad muscles of the abdomen, furnish a 

 lateral cutaneous branch to the integument of the hip, and becoming subcutaneous 

 anteriorly, end in the integument of the lowest part of the abdomen and scrotum in 

 the male, or labium pudendi in the female, as well as the adjacent part of the 



