ACTIONS OF THE ABDOMINAL MUSCLES. 32-'? 



If the vcitebial column be fixed, these muscles press np tlie diaphragm througli 

 the abdominal viscera, draw down the ribs, and contract the lower border of the 

 thorax, and so contribute to expiration ; but if the vertebral column be not fixed, 

 the thorax will be bent directly forwards, when the muscles of both sides act, or 

 xotated to either side, should they act alternately. 



Fig. 227. 



Eig. 227. DiAGKAM OF A TRANSVERSE SECTION OP THE WaLL OP THE AdDOMEN, To 



SHOW THE CONNECTIONS OF THE LuMBAR AND AliDUMINAL APONEUROSIS, AND THE 



Sheath of the Rectus Muscle. (A. T. ) ^ 



A, at the level of the tbird lumbar vertebra ; B, the fore part, at a few inches above 

 the pubes. 



a, .spinous process of the third lumbar vertebra ; h, body ; 1, external obliqne muscle ; 

 ■2. internal oblique ; 3, transversalis ; 4, a dotted line to mark the position of the fascia 

 lining the abdomen ; 5, 5, in A, the anterior and posterior parts of the sheath of the 

 rectus, formed liy the aponeurosis of the internal oblique splitting at its outer edge 2' ; 

 6, the rectus abdominis ; 7, innermost layer of the aponeurosis, covering iu front the 

 quadratus lumborum, and passing to the root of the transverse process : S, the psoas 

 magnus and parvus muscles ; 9, the erectores spinie muscles ; 9 + , the middle layer of 

 the lumb.ar aponeurosis passing to tlie extremity of the tranverse process ; 10, 10 +, the 

 posterior layer of the lumbar aponeurosis, connected with the latissimus dorsi and serratus 

 inferior : in A, at the sheath of the rectus, the aponeurosis of the external oblique is 

 seen to unite in front Avith the sheath, while that of the transversalis is seen uniting 

 with it behind : in B, the section is taken below the semilunar fold of Douglas, where 

 all the tendons pass in front of tlie rectus as at 5' ; the + near this, and in a similar 

 place in A, marks the middle line, and the place of the union of the several aponeuroses 

 in the linea alba. 



If the thorax be fixed, the abdominal muscles may be made to act on the 

 pelvis ; thus, in the action of climbing, the trunk and arms being elevated and 

 fixed, the pelvis is drawn upwards, either directly or to one side, as a preparatory 

 .step to the elevation of the lower limbs. 



The attachment of the tendinous intersections of the rectus muscle to tho 



