THE MUSCLES 75 



'oblique' and 'straight' portions respectively, of a common muscle, 

 since the innervation is virtually the same in each case. 



The straight portion consists of two flat sheets of muscle arising 

 from the lateral faces of the expanded ends of the first two ribs. The 

 fibres pass directly dorsalwards and are inserted on the dorso-mesial 

 border of the suprascapula. 



Innervation: From the NN. thoracici superiores of the second, 

 third, and fourth spinal nerves. 



Function : The muscles serve to depress the scapula and thus cause 

 the ventral portion of the pectoral girdle to expand. 



The oblique -portion again consists of two sections. The anterior 

 of these arises from the lateral face of the second rib, just ventral to 

 the straight portion. It passes anteriorly, inclined slightly dorsal- 

 wards, and is inserted on the antero-mesial border of the supra- 

 scapula. The second portion arises by three heads from the third, 

 fourth, and fifth ribs. These unite into a single bundle passing antero- 

 dorsally to be inserted on the postero-dorsal angle of the suprascapula. 

 This portion of the muscle lies deep to the M. dorso-humeralis. 



Innervation: As above. 



Function : It serves to retract the scapula, while the general func- 

 tion of the M. thoraci-scapularis as a whole is to attach the pectoral 

 girdle to the axial skeleton, thus forming an elastic suspension for 

 the anterior part of the body. 



The muscles associated with the ventral half of the pectoral girdle 

 are all inserted in the limb, and are therefore considered in the 

 sections which follow (PI. VI I, figs. 43 and 45). 



3. Muscles of the Arm.^ 



M. pectoralis (m.p.). Schmidt, Goddard, and van d. Hoeven (i 864) ; 

 Owen (1866); Mivart (1869); Humphry (1872); Furbringer 

 (1873); Hoffmann (1873-8); Rylkoff (1924). 



Grand pectoral ....... Cuvier (1800). 



Portio inferior m. pectoralis majoris . . . . Funk (1827). 



Grosser Brustmuskel Meckel (1828). 



Abdomino-coraco-humeral, portion du grand pectoral Duges (1834), 



Pectoralis major . . . Stannius (1854-6); Rudinger (1868). 



Pectoralis sternalis +pectoralis abdominalis . . Eisler (1895), 



Tete sternale; flechisseur du bras (86) . . . Perrin (1899). 



Together with MM. supracoracoideus and procoraco-humeralis = 



Pectoralis magnus + Pectoralis magnus, pars anterior . Carus (1828). 



' As in the case of the skeleton the proximal joint of the limb is referred to as the 

 'arm', and the distal joint as the 'fore-arm'. 



