THE ABDOMEN." 



375 



on this fibrous layer but are too small to cause troublesome hemorrhage; a few 

 minutes' compression with haemostatic forceps serves to stop bleeding from them. 

 This layer is attached at the linea alba, but not sufficiently closely to prevent 

 extravasated urine from crossing and reaching both flanks. It is also attached to the 

 fascia lata just below Poupart's ligament, and here it does prevent urine from passing 

 downward on the thigh. It passes inward over the spermatic cord and is continuous 

 with the dartos of the scrotum and its septum. It is attached to the spines of the 

 pubes and to the symphysis in the median line. This leaves a space or abdomino- 

 scrotal opening over the pubic bone on each side of the median line through which 

 extravasated urine rises from the perineum and scrotum to reach the surface of the 

 abdomen. 



MUSCLES OF THE ABDOMEN. 



The muscles of the abdomen are arranged in two distinct groups : a longi- 

 tudinal group embracing the recti and pyramidales and a transverse group embrac- 

 ing the external and internal oblique and the transversalis of each side. 



The pyramidalis is small, often undeveloped, and sometimes absent ; as its 



External oblique 



Lineae transversae 



jCj Rectus abdominis 



Sheath of the rectus 

 turned back 



Umbilicus 



Pyramidalis 



External abdominal ring 



Spine of the pubis 



External pillar 

 Spermatic cord 



FIG. 387. The external oblique, rectus abdominis, and pyramidalis muscles. 



direction is not markedly different from that of the rectus it may be considered from 

 a surgical point of view as being a part of it. 



The rectus muscle arises from the crest and symphysis of the pubis and 

 inserts into the cartilages of the fifth, sixth, and seventh ribs and sometimes the 

 ensiform cartilage (Fig. 387). 



Sheath of the Rectus. The rectus muscle is enclosed in a fibrous sheath formed 

 by the external and internal oblique and transversalis muscles. The anterior layer 

 is attached to the surface of the muscle by the lineae transversae already described 

 (p. 372). The edge of the sheath on one side blends in the median line with that of 

 the other side to form the linea alba. Above the umbilicus, an incision in the 

 median line passes through fibrous tissues only and the muscles on each side are not 



