MUSCLES OF THE ABDOMEN. 389 



ternal oblique before. Being fixed in the sheath formed by the 

 separation of the tendon of the transversalis muscle it tapers to 

 a point above, and is inserted into the linea alba and internal 

 edge of the rectus, for about the upper two-thirds of its own 

 length. 



It strengthens the lower part of the abdomen.* 

 At the linea semilunaris the tendon of the internal oblique 

 and of the transversalis unite intimately; and just beyond this 

 junction the two laminae are formed, which enclose the rectus 

 muscle. The anterior lamina is one half of the tendon of the 

 internal oblique, which, after passing half an inch or an inch, is 

 joined to the tendon of the external oblique, goes in front of the 

 rectus muscle, and covers it from origin to insertion. The 

 posterior lamina, made by the posterior half of the tendon of 

 the internal oblique, is united already at the linea semilunaris to 

 the tendon of the transversalis: in this manner they pass behind 

 the rectus muscle from the cartilago-ensiformis to a line half- 

 way between the umbilicus and the pubes. From this line, 

 downwards, all the tendons go in front of the rectus muscle. 



The obliquus externus tendon may be dissected from the 

 common tendon of the others, without much difficulty, almost 

 to the linea alba. The term insertion, expresses, very imper- 

 fectly, the manner in which the tendons of these broad muscles 

 all terminate in the linea alba from the thorax to the pelvis. 

 It should rather be said, that they coalesce there by a general 

 intertexture of their fibres. 



The Cremasler, 



Is commonly attributed exclusively to the internal oblique, 

 as it is said to be a detachment of fibres from it; but it is also 

 formed by fibres from the lower edge of the transversalis mus- 

 cle. The history of its formation is as follows: in the descent 

 of the testicle, the latter has to pass beneath that edge of the 

 transversalis and of the internal oblique which is extended from 

 the outer portion of Poupart's ligament, to the spine and crista 



* Varieties. It is frequently defective, but sometimes two, three, or even four, 

 are seen on a side. When defective, the rectus or obliquus internus is better 

 developed than usual. 



33* 



