cas) 
~? 
Or 
Charles R. Bardeen 
37.7% from the 20th and 21st spinal nerves; and 32.7% from the 21st 
spinal nerve. The inguinal nerve arose from the 20th spinal nerve in 
3.5% of instances; from the 20th and 21st in 38.3%.; from the 21st in 
51.5% ; and was absent in 6.6%. The genito-femoral nerves arose 
from the 21st spinal nerve in 19% of instances; from the 21st and 22d 
in 79% of instances; and from the (21st) 22d and 23d in 2% of in- 
stances. In 1.2% of instances no lumbo-inguinal (crural) branch was 
found. It is probable that the variation in origin of the border nerves 
is due in part to a variation in position of the base of the limb-bud with 
respect to the spinal column, the more anterior spinal nerves serving to 
supply the limb when the limb-bud has a more anterior position at the 
time of the outgrowth of the spinal nerves. There is, however, no perfect 
correspondence between variation in origin of individual border nerves 
and that of the border nerves as a group. 
In the same paper I showed that out of 133 instances, in 27 (20.30%) 
the lumbo-inguinal (crural) nerve emerged from the pelvis into the thigh 
in a lateral (external) region; in 81 instances (60.9%) in the middle 
(anterior) region; and in 25 instances (18.8%) in a medial (internal) 
region. After the nerve has passed into the thigh it may have a slight, a 
moderate or an extensive distribution to the skin. While this distribution 
usually corresponds to the region of exit, lateral, middle or medial, this 
is not always the case. Jor instance, a nerve emerging laterally may 
send a branch over to supply the fascia on the medial side of the leg. The 
following table indicates the frequency and extent of distribution of the 
lumbo-inguinal nerve to the skin of the lateral, anterior and medial por- 
tions of the thigh. By “lateral” region is meant an area lying lateral 
to a line drawn from the anterior inferior spine of the ilium to the 
lateral edge of the patella; by “ medial,” an area lying medial to a line 
drawn from the medial margin of the hip joint to the medial edge of the 
patella; and by “anterior,” the intervening area. By “slight distribu- 
tion” it is meant that by gross dissection the branches of the nerve could 
be followed but a short distance below the inguinal hgament; by “ ex- 
tensive distribution” it is meant that the branches could be followed 
readily over half way down the thigh. By “ moderate distribution ” is 
meant a distribution lying between these extremes. It will be understood, 
of course, that no hard-and-fast lines can be drawn between the various 
types of distribution tabulated. The table is intended merely to give an 
idea of the approximate frequency of distribution of the lumbo-inguinal 
nerve to approximate areas. 
19 
