28 
PRIMROSE : THE ANATOMY OF THE ORANG OUTANG 
of the sixth costal cartilage running under the lower border of the pec- 
toralis major, it passed down the arm and was inserted into the intermus- 
cular septum two inches above the internal condyle. 
The Pectoralis minor {^X'dXQ IV, fig. 2,/. min'), arose from the bone of the 
fourth rib by an origin 2 cm. wide, immediately external to the cartilage, 
and from the bone and cartilage of the third rib by an origin of similar 
width. The muscle was inserted into the superior and inner part of the 
coracoid process of the scapula. Certain fibres of the tendon of 
insertion were carried on beyond the coracoid and were definitely traced 
as two ligamentous structures which diverged from one another, one of 
which was attached to the outer end of the clavicle, and the other into 
the acromion process of the scapula (see plate IV, fig. 2, and fig. 3, lig. 7, 
lig. 2), the insertion here described has not hitherto been demonstrated, 
and it would appear to be an observation of some interest. Duvernoy^ 
states that in the Chimpanzee the pectoralis minor became attached to 
the coraco-clavicular ligament ; again whilst I found no description of 
an acromial attachment among the anthropoid apes I find that in 
Cynocephalus, according to Bischofif^ the pectoralis minor is inserted 
into the coracoid process and the coraco-clavicular ligament. In the 
Chimpanzee we find that Huxley, Pick, Bischoff, Hepburn and others 
have described an insertion into the capsule of the shoulder joint. It 
is not unusual to find this capsular attachment in man. This relation 
of the pectoralis minor to the capsule, in certain cases occurring in man 
and monkeys, induces Bland Sutton to believe that the coraco-humeral 
ligament of the shoulder joint is the tendon of the pectoralis minor 
muscle transformed into a fibrous band. But as the insertion varies so 
greatly in apes it would seem that Bland Sutton is not warranted in 
coming to the conclusion he does. Hepburn found that in the Gibbon 
in addition to a coracoid and a clavicular attachment, the muscle was 
inserted into the common tendon of the coraco-brachialis and biceps 
a short distance below the tip of the coracoid process. Whilst in the 
Chimpanzee both Huxley® and Hepburn describe the muscle as uniting 
with the supra-spinatus. Judging from the attachments described 
in my Orang, and from the relations found in some other apes and the 
variations in man, it may be that the trapezoid portion of the coraco- 
clavicular ligament and the coraco-acromial ligament are in part derived 
1 Loc cit., p. 76. 
2 Loc, cit., I, p. 209, 
3 J. Bland Sutton, “ Ligaments, their Nature and Morphology.” London, 1887, p. 71. 
4 Loc. cit., p. 154. 
5 Loc. cit., Vol. I, p. 456. 
