EXAMINATION OF SOME SPINAL NERVES 113 
the fact that hroad sitnilarity of requirement and use he/s, from broadly ihnilar segmental material^ 
evolved^ at two places of the ventro-lateral aspect of the quadruped, two separate structures so curiously 
alike as are the brachial and the pelvic limbs. The details of this resemblance between the two 
appear to me absolutely insufficient criteria for establishing detailed homologies between their 
parts. 
Anatomists teach* that in the higher vertebrata, at an early period of the embryonic 
existence of the limbs, a rotation of the limb, as a whole, takes place at its place of junction with 
the trunk. This rotation, at the proximal end of the limb, is described as occurring in opposite 
directions in the fore and hind limbs respectiveh'. The fore-limb is rotated from the shoulder 
through nearly a quarter of a circle, so that the convexity of the elbow, which should point 
dorsally, comes to point backwards, and the edge, called by Huxley the post-axial (in reference to 
the axis of the limb itself), instead of being directed backward, is directed inward towards the 
middle line of the body. The pre-axial edge of the fore-limb is conversely turned laterally outward. 
At the same time the hind-limb is supposed to be rotated from the hip through 90° forwards ; the 
knee, thereafter, instead of presenting its convexity dorsally, presents it toward the front, and the 
pre-axial border of the limb is, therefore, turned inward toward the ventral surface of the body, the 
post-axial edge laterally outward. The view of the position of the limbs of the Cat and Monkey, 
to which the observations in my own papers point, does not correspond with the above. The 
analysis of the spinal nerve-root distribution, as insisted previously, shows the Monkey's limbs to be 
built up exactly on the plan of a lateral fin. The most definite pieces of surface to use as criteria 
to the topography of the limb are the mid-dorsal and mid-ventral lines above described. The pre- 
axial and post-axial borders of the limbs, which I liave thought it clearer to speak of as anterior 
and posterior simply, are lost as borders where portions of the limbs become cylindrical, and this 
can be broadly said to have occurred in the upper arm, forearm, thigh, and leg of the Monkey ; 
they never existed as borders in the attached bases of the limbs where the sessile limb-bud is fused 
with the trunk. It is therefore only in the hand and foot that these borders persist as borders, 
and there they meet, so that the point where posterior border ends and anterior begins can only 
be approximately decided. According to the received view, the pre-axial border contains in the 
fore-limb the outer condyle and greater tuberosity of the humerus, in the hind-limb the inner 
condyle and the lesser trochanter of the femur. How far such deep-lying structures as two of 
the above can be parts of any ' border ' of the limb is not to me clear ; be that as it may, the 
nerve-supply of the limb, as now analyzed, shows that the above-named two points in the upper 
limb lie but little in front of the mid-dorsal line of the limb, and very greatly nearer to it than to 
the mid-ventral line of the limb, and can, for this reason, hardly be considered to lie in an anterior 
(pre-axial) surface of the limb, still less to constitute points in the pre-axial (anterior) border of 
the limb. Again, the two above-named points in the lower limb lie under the mid-ventral line 
of that limb, and are not parts of its pre-axial (anterior) surface, still less of its pre-axial (anterior) 
border. The point of the knee is by my evidence brought to belong to the anterior (pre-axial) 
* Cf. Flower and Gadow. ' Osteology of Mammalia,' p. 361, &c. 
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