PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
37 
the muscle the fibres were very oblique, arising from the ulna as high up 
as the upper portion of the lower fourth, and passing obliquely down- 
wards and outwards to the radius. The obliquity of the fibres was also 
noted by Pick. 
The Supinator longus arose from the supracondyloid ridge of the 
humerus as high as the middle of the bone, and extended down to 
within 2.5 cm. of the external condyle. It was inserted into the outer 
aspect of the lower extremity of the radius, including the styloid process, 
the whole insertion being 2.5 cm. wide. In Pick’s Orang the insertion 
began 7 cm. above the styloid process. In the Gibbon, Bischofif found it 
short, not reaching to the styloid process but inserted into the middle of 
the bone. A similar condition was found in the Gibbon by Huxley.^ 
In man the muscle has been found inserted as high up as the middle 
third of the radius. 
The Supinator hrevis and Anconeus were well developed, and re- 
sembled in their connections and relations the condition found in man, 
in other anthropoids and in the lower apes. 
The Extensor carpi radialis longior arose below the supinator longus 
from the supra condyloid ridge of the humerus as low as the external 
condyle. It passed under the annular ligament in company with the 
short radial extensor and was inserted into the dorso-radial aspect of the 
base of the second metacarpal bone. 
The Extensor carpi radialis brevior arose from the common extensor 
origin from the external condyle, and was inserted into the dorsal aspect 
of the base of the third metacarpal bone. The two radial extensors were 
crossed obliquely by the short and long extensors of the thumb and the 
extensor ossis metacarpi pollicis ; they resembled in their relations and 
connections the condition found in man and in the lower and the anthro- 
poid apes. 
The Extensor com^nunis digitorum arose from the common extensor 
origin, and passed under the annular ligament in company with the ex- 
tensor indicis ; it divided into four tendons for insertion into the four 
inner digits as in man. 
The Extensor minimi digiti was a very small fasciculus arising in 
common with the extensor communis ; it was inserted into the extensor 
expansion over the proximal phalanx of the ring and the little fingers. 
One finds that the slip to the ring finger occurs as a variety in man, 
Loc. cit., Vol. I, p. 648. 
