MUSCLES OF THE TRUNK. 67 



II. MUSCLES OF THE TRUNK. 



I. Muscles of the Abdomen. 



In the formation of the abdominal wall the following muscles 

 take part : — (i) m. rectus ahdominis, (2) m. oU'iquus exteruus, (3) m. 

 ohliqiins internus, (4) the port'm abdoininalis of the m. pecforalis. 

 Above, the m. obliqiins Intermis forms a kind of diaphragm, partially 

 separating" the abdominal from the thoracic cavity (p. 70). 



28. M. rectus atjâomïnis (Fig. 62 /•). 



Dugès, pubio-thoracique, n. 52. 



These muscles, situated on either side of the middle line of the 

 abdomen, are as a rule traversed by five notched 'mscripf tones ten- 

 (lineae. Each muscle arises, by a narrow, strong tendon, from the 

 inferior border of the pubes, passes forwards, and quickly ■«àdening, 

 divides at the second inscripiio iendinea (counting from behind) into 

 two portions. 



{a) The Outer portion (Fig. 62 r) runs into the port'io abdommaUs of 

 the m. pectoralis, and forms the greater lateral division of that muscle. 



{Ij) The Inner (;•') continues as the m. rectus ahdominis and gradu- 

 ally narrows anteriorly. At the sternum some of the fibres (the 

 median) are inserted into the dorsal surface of the cartilaginous 

 plate of the xiphisternum, while the greater part of the muscle con- 

 tinues forwards over the coracoid to become the m. sternohijoideus 

 at about the fifth inscrlpt'w iendinea (p. 64). 



29. M. ohliquus exiernus (Fig. 63 oe, oe'). 



Zenker, I.e., p. 31, m. ohliquus. — Dugès, dorso-sous-abdominal, n. 54. 



The ni. otjiiquus exfernus arises from — 



(r/) The aponeurosis covering the long muscles of the back, and 

 by this from the spinous processes. The anterior edg'e of the 

 VI. oJjliquns exfernus covers the posterior edge of the m. lafissimus 

 dorsi, which arises from the inferior, ventral surface of the aponeu- 

 rosis. The aponeurosis also divides laterally into two parts, one of 

 which, the posterior, passes into the ohliquus exiernus, while the 

 anterior forms the tendon of origin of the dejiressor maxillae Inf. 

 [dm) (compare Fig. 66). 



ijj) A second, narrow portion, porilo onw-ahdomlnalis (Fig. 63 oe') 



F 3 



