76 THE SALAMANDER 



The M. pectoralis is a large, superficial, fan-shaped plate of muscle 

 covering the posterior region of the breast. Its anterior fibres are 

 approximately transverse to the vertebral axis and gradually become 

 more and more oblique until eventually the posterior ones are almost 

 longitudinal. The muscle has a varied origin. Anteriorly the fibres 

 lying ventral to the coracoid arise from a median aponeurosis separat- 

 ing the muscles of the right and left sides, next a few fibres arise 

 from the sternal plate, then follows a section which takes its origin 

 from the wide aponeurosis of the M. obliquus externus superficialis, 

 and finally the most posterior fibres of all are continuous with 

 those of the M. rectus abdominis superficialis. All the fibres con- 

 verge to a strong tendon, which is inserted, together with that of the 

 M. supra-coracoideus, on the posterior aspect of the crista ventralis 

 humeri. 



Innervation : By the N. pectoralis which arises from the fourth (or 

 fourth and fifth) spinal nerve and enters the posterior portion of the 

 muscle on its mesial aspect. 



Function: To draw the arm inwards towards the body and pos- 

 teriorly, or if the hand is resting on the ground, to advance the body. 



MM. supracoracoideus and coraco-radialisproprius. Furbringer (1873); 

 Hoffmann (1873-8); Osawa(i902). 



These two muscle slips are very difficult to separate, and in fact their 

 separation must be regarded as largely artificial, while they are most 

 clearly distinguished by their insertions. 



(a) M. supracoracoideus (m.s.c). Osawa (1902); Rylkoff (1924). 



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



Einwartszieher, Theil des grossen Brustmuskels . Meckel (1828). 



Clavi-humeral, portion du grand pectoral . . . Duges (1834). 



Pectoralis secundus ..... Stannius (1854-6). 



Pectoralis minor . Schmidt, Goddard, and van d. Hoeven (1864). 



Part of pectoralis ....... Owen (1866). 



Coraco-brachialis proprius .... Riidinger (1868). 



First part of coraco-brachialis ..... Mivart (1869). 



Epicoraco-humeral. ..... Humphry (1872). 



The more superficial of the two slips arises from the ventral surface 

 of the cartilaginous portion of the coracoid, with the exception of the 

 posterior third. Its fibres converge to a flat tendon, which is inserted, 

 together with that of the M. pectoralis, on the posterior face of the 

 crista ventralis humeri. The posterior half of the muscle is covered 

 by the M. pectoralis. 



