302 THE MYOLOGY OF THE RAVEN. 



the ribs, soon gives way afc the lower thirds of the 

 ribs to a fleshy layer of transverse muscular fibres 

 which are well developed. These in turn are also 

 more or less attached to the ribs beneath them, along 

 on their line of commencement below the epipleural 

 appendages. The muscular sheet thus formed passes 

 toward the sternum, loosely attached by fascia to the 

 hsemapophyses, overlying and concealing the latter 

 from sight as it does so. Again becoming aponeu- 

 rotic, it becomes attached to the side of the 

 sternum, and quite firmly so to the under side 

 of the lower part of the pectoralis major muscle 

 and the xiphoidal prolongation beneath it. The 

 transverse fibres of this muscular sheet extend down 

 the abdomen, and are continuous with those arising 

 from the edge of the posterior moiety of the post- 

 pubic element of the pelvis already alluded to above. 

 The muscular fibres of the abdominal portion pass 

 somewhat downwards, though nearly transversel} 7 ", to 

 the median abdominal line, where they terminate in 

 an aponeurosis just before arriving at the linea alba 

 For the upper two-thirds of the abdomen in the median 

 line, the aponeurotic fibres decussate, and are quite 

 firmly attached to the skin. 



Owen says that in the Apteryx " the aponeurosis from 

 the last rib passes to be inserted into a strong ligament 

 extending between the free extremities of the pubic 

 bones, leaving the abdomen, behind the last rib, de- 

 fended only by the internal oblique and transver- 

 salis." As I have already said, in the Eaven the very 

 delicate aponeurosis of the external oblique extends 

 into this recess between the last rib and the pelvis, 

 to become attached in the manner I have already 

 described. 



