34 
PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
then crossed obliquely behind the other tendons to reach the index 
finger. The fasciculus is joined at an acute angle by a few fibres 
from the radial origin; this radial fasciculus represented not more 
than one-twentieth part of the main fasciculus, being a very slender, 
though definite contribution. In Bischoff’s Gorilla there were four 
almost completely separated muscles having an arrangement similar 
to that found in my Orang. This differs from the muscle dissected by 
Pick in his Orang, in which there was a superficial fasciculus passing to 
the fourth and fifth digits, and a deep fasciculus to the second and third 
digits. The muscle in man is developed in two layers, more or less 
separable from one another, the superficial passing to the third and 
fourth, and the deep to the second and fifth digits. 
The Flexor profundus digitorurn vel Perforans arose by three distinct 
fasciculi. 
1. From the anterior and inner aspects of the ulna extending back to 
the posterior border and upwards as high as the posterior portion of 
the olecranon process, and downwards on the ulna to about its middle. 
(The nerve supply was from' the ulnar.) 
2. From the anterior aspect of the ulna up to and including the lower 
part of the coronoid process ; from the anterior and inner border of the 
ulna below the fasciculus I. and from the interosseous membrane. (The 
nerve supply was the median.) 
3. From the anterior aspect of the radius, and from the interosseous 
membrane ; this radial attachment extends two-thirds of the way down 
the bone. In the middle third, well over to the radial border, its attach- 
ment is limited by the origin' of the flexor sublimis digitorum. (The 
nerve supply was from the median.) 
The tendons passed under the annular ligament, and fasciculus No. i 
supplied tendons to the minimus and the ring fingers ; fasciculus No. 2 
to the middle finger, and fasciculus No. 3 to the index finger. A 
lumbrical muscle was developed on the radial side of each tendon in the 
palm. Rudolf traced the nerve supply of the lumbricals, and found the 
outer two were supplied by the median and the inner two by the ulnar 
nerve. 
There was no trace of a long flexor for the thumb. In this particular 
man differs very markedly from the Orang. In man the flexor longus 
pollicis is a separate well developed muscle, and nothing approaching it 
