PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 345 



The 2yectoralis minor appears to vary considerably both in origin 

 and insertion. In my specimen it arises by three well-marked 

 slips from the lower borders of the second, third, and fovirth 

 costal cartilages. Its long, but strong, tendon passes through 

 a fibrous and synovial sheath over the coracoid process, and it is 

 inserted into the upper and back part of the capsule of the 

 shoulder joint. The sheath is adherent to the inner and upper 

 parts of the coracoid process. Champneys (11) gives its origin 

 from the first four ribs and its insertion into the capsule of the 

 shoulder joint close to tlie supra-spinatus tendon, and Humphry 

 (26) mentions it as extending across to the great tuberosity of 

 the humerus. Bland-Sutton (4) describes an insertion similar to 

 that in my specimen, but gives its origin as I'ibs three, four, and 

 five. Wilder (53) and Gratiolet (22) record tendons inserted 

 into both tlie coracoid process and capsule of the shoulder joint, 

 and the latter gives the origin as ribs two to five inclusive. So 

 if several animals are examined the muscle appears to write its 

 evolutionary history. 



The sej'ratus magnus arises by eleven digitations from the first 

 eleven ribs, the first one being very small, but it has a remark- 

 ably rich supply of nerves (text-fig. 48). The first nine arise 

 from the outer surfaces of the ribs, but tlie tenth and eleventh 

 arise from the lower borders. The digitations arising from the 

 fifth to the eleventh ribs interdigitate with the external oblique. 

 The muscle is thick at its insertion into the deep aspect of the 

 vertebral border of the scapula. The part arising from the first 

 four ribs is much thinner than the remaining part of the muscle. 

 Champneys (11) has given the origin as from the first ten ribs, 

 and described the muscle as consisting of three parts, which he 

 describes in great detail, but Wilder (53) describes two parts, 

 and gives the origin from all the ribs. 



The suhclavius arises from the upper border of the first costal 

 cartilage immediately internal to the rib. It is inserted into 

 the under surface of the second quarter of the clavicle from 

 the inner end. It is enveloped as in Man by the costo-coracoid 

 membrane. 



The costo-coracoid memhrane is attached to the first costal 

 cartilage round the tendon of origin of the suhclavius, to the 

 inferior surface of the sterno-clavicular joint, to the under sur- 

 face of the clavicle by two layers which enclose suhclavius as in 

 Man, and to the anterior surface of the clavicle lateral to the 

 suhclavius. The costo-coracoid ligament is well marked. Several 

 authors have recorded the latter. The clavi-pectoral fascia ex- 

 tending downwards from the costo-coracoid ligament splits to 

 enclose the pectoralis minor, and at the same time it sends a 

 process inwards to the neuro-muscular bundle in the axilla. 

 External to the pectoralis minor the fascia passes to the deep 

 fascia of the axilla, and it passes mesially to the deep fascia 

 covering the serratus magnus betv/een the pectoralis major 

 and latissimus dorsi. The membrane is pierced by the external 



