AKT. 13 BKACHIAL. FLEXOES IN" PRIMATES HOWELL AND STRAUS 6 



repeatedly found. Yet it is so easily mistaken either for a part of 

 the brachialis or of the coracobraehialis, according to variations in 

 other details, that it will be mentioned. In this chimpanzee it was 

 quite robust, arising from the entepicondyloid ridge and inserting 

 fleshily upon the olecranon. 



Pan sp. — Left side. 



M. biceps hrachii, capita longu^n et breve. — Origin of the caput 

 longum had three separate attachments, two as on the right side and 

 the third almost as tendinous as, and covering, the proprius origin. 

 Also the tendinous part of the origins of both biceps divisions was 

 markedly shorter (more fleshy) than on the right. Upon the latter 

 side the broadest part of the biceps (at the distal third) was 36 mm.; 

 upon the left, 60 mm. Other details were bilaterally similar. 



M. co7'acobrachialis 7nedius. — This had the usual origin from the 

 deep part of the common coracoid tendon but was slightly broader 

 than on the right and more flesh}^ The medial part of the origin 

 continued superficial to the musculocutaneous nerve, while the re- 

 mainder, or more lateral part of origin, passed deep to the nerve. 

 The latter therefore pierced the muscle, and at this point the two 

 parts of the muscle were about of the same mass. The part located 

 deep to the nerve was inserted narrowly (less than 1 cm.) imme- 

 diately below the latissimus tendon, but the more medial portion was 

 continued as a narrow, fibrous band distal to the other head. With 

 the exception of this tendon there was a hiatus of some 18 mm. 

 between the insertions of the two parts of the coracobraehialis, and 

 the division superficial to the nerve thereafter inserted upon the 

 humeral shaft for a distance of some 30 mm. In the vicinity of the 

 elbow the median nerve passed superficial to all parts of the coraco- 

 braehialis. 



The remainder of the flexor details were similar to those of the 

 right side. 



Hylobates lar. — Johns Hopldns Anat. No. 261, male, with 

 humeral length of 215 mm. ; right and left sides. 



M. biceps brachii^ capita longwn et hmnerale. — In this gibbon the 

 long head had a normal origin from the glenoid border of the scapula, 

 except that the tendon was hollow, taking a stout probe for its full 

 length, and this tendinous cylinder was naturally split along one side 

 where the muscle fibers began. It inserted by a strong tendon upon 

 the radius. The other head, termed humerale rather than breve for 

 the reason that it differed markedly from the latter and that there is 

 no absolute assurance that it was derived from the more usual breve, 

 took origin not from the coracoid, but by tendon from the lesser 

 tuberosity immediately adjoining the bicipital groove. Its tendon 



