542 MUSCLES OF THE ABDOMEN. 



ovally-curved lines upon each side, and about three Inches 

 distant from the linea alba, formed by the splitting of the 

 tendon of the internal oblique, where it proceeds to form a 

 sheath for the rectus muscle. The linece transversce are three 

 or four short lines, going from the linea alba transversely 

 across the rectus muscle, to the lineae semilunares ; one of 

 these lines is seen at the umbilicus, another at the lower 

 end of the ensiform cartilage, a third between these two 

 points, and sometimes a fourth midway the navel and pubis. 



The external abdominal ring (Fig. 168) is situated in the 

 lower part of the tendon of the external oblique, superior 

 and external to the spine of the pubis upon each side, above 

 Poupart's ligament. This ring (improperly so called)- is 

 triangular in form, having its base toward the pubis, and 

 its apex external and superior. The sides of this opening 

 are termed columns or pillars, superior and inferior. The 

 superior column is broad, and its fibres go to the sym- 

 physis pubis, and decussate with those of its fellow in front 

 of the pubis and dorsum of the penis. The inferior 

 column, called also the pubic end of Poupart's ligament, or 

 third insertion of the external oblique, goes to the spine of 

 the pubis and about an inch along its crest. 



This ring varies as to size ; it is larger in the male than 

 the female, its average dimensions being from an inch, to 

 an inch and a half in the longest direction, and about half 

 an inch transversely. This opening is very interesting 

 from the fact of its transmitting in the male the spermatic 

 cord and cremaster muscle, and in the female the round 

 ligament of the uterus, and particularly so to the surgeon, 

 from being the seat of that form of hernia called oblique 

 inguinal. 



Function. Tlte external oblique assists in expiration by 

 compressing the abdominal viscera, which press up the 

 diaphragm, and thus diminish the thoracic cavity. It also 

 aids in evacuating the foeces and urine, and brings the 

 thorax and pelvis toward each other. 



Internal oblique obliquus internus abdominis ascendens. 

 (Fig. 167.) Dissection. Kemove the external oblique by an 



