SHEATH OF RECTUS MUSCLE 97 



abdominal viscera and expel the contents of those which are 

 hollow. 



The fibers from the inguinal ligament, of both internal oblique and trans- 

 versus muscles, arch downward to the pubes. 



SHEATH OF THE RECTUS ABDOMINIS (FIGS. 79, 80) 



In the lower fourth of the linea semilunaris, the entire thick- 

 ness is continued forward as one layer in front of the muscles. 

 In the upper three-fourths the linea semilunaris divides into two 

 layers which meet again in the linea alba; thus a compartment is 

 formed to be occupied by the rectus muscle. 



This is called the sheath of the rectus, with its anterior and 

 posterior layers, the anterior layer being thickest and strongest in 

 the lower part where the greatest strain would be brought upon it. 



Lineae transversae (transverse lines). At three different levels 

 above the umbilicus the anterior ayer of the sheath is held down 

 to the rectus muscle by fibers forming transverse lines. 



Note. The location of all these markings the semilunar line, the white 

 line, and the three transverse may be seen on the surface of the body during 

 the action of the muscles; and in a piece of statuary representing the trunk 

 they should be plainly indicated (Fig. 79). 



FIG. 81. THE DIAPHRAGM. 

 Dotted lines indicate descent in contraction. (H olden ) 



ROOF OF THE ABDOMEN 



The roof of the abdomen is the diaphragm; it has no floor of 

 its own, the pelvic floor serving for both cavities (page no). 

 The diaphragm. This is a broad, thin, dome-shaped muscle 



7 



