Charles R. Bardeen Hil 
Oo 
above, p. 302. The nerve for the obturator externus usually arises before 
the obturator nerve enters the obturator foramen. The nerve generally 
divides into two branches, one of which enters the superior border of the 
muscle, and the other passes to its external surface. 
Some of the superior fasciculi of the obturator externus muscle may 
be separated from the main belly by the obturator nerve or its deep 
branch. 
Adductor magnus. Plate II, Fig. 3; Plate VIII, Figs. 1 and 2. This 
muscle is developed from two distinct anlages, to one of which a branch 
from the obturator nerve is given, and to the other a branch from the 
sciatic nerve. These anlages are distinct in an embryo of 14 mm., but in 
one of 20 mm. (Plate VIII, Fig. 3) they have fused and a rearrangement 
of tissue has begun so that the three divisions of the muscle described 
by Poirier‘ are beginning to be distinct. The exact steps in this 
rearrangement of tissues I have been unable clearly to follow in the 
material at my disposal. In the adult muscle the obturator nerve usually 
gives off one or more branches which enter the main body of the superior 
division of the muscle, the adductor minimus, on its obturator surface 
about midway between the tendons of origin and insertion, and several 
branches which pass in between the larger fasciculi of the middle and 
inferior divisions of the muscle about midway between their tendons of 
origin and insertion. The branch from the sciatic nerve likewise enters 
between the main muscle bundles on the posterior surface of the middle 
and inferior divisions of the muscle about midway between their tendons 
of origin and insertion and usually sends a recurrent branch into the 
lower border of the superior division of the muscle. Not infrequently 
the nerve to the quadratus femoris muscle sends a branch into the upper 
margin of the superior division of the adductor magnus. In one instance 
a special branch of the sciatic was given to this portion of the muscle. 
There is nothing to indicate that either the obturator or the sciatic 
branch is confined in its distribution to the tissue of the muscle mass to 
which it is originally sent. On the contrary it is exceedingly probable 
that the sciatic branch helps to innervate a portion of the obturator 
muscle mass and the obturator branch a portion of the sciatic muscle 
mass. 
CoMPARATIVE ANATOMY AND VARIATION IN THE ADDUCTOR GROUP. 
In this group are included the obturator externus and the three adductor 
muscles. The pectineus also belongs anatomically and physiologically and 
probably in part also morphologically with this group (see p. 303). The 
*Traité d’Anatomie, Tome 2, p. 229. 
