THE ABDOMEN. 221 



scattered tendinous fibres apparently belonging to the 

 internal oblique muscle. Having removed these we see'^ 

 trausversalis abdominis, on the external surface of which 

 certain nerves rendered consinciious by their tvhiteness run- 

 directly from the intervertebral lumhar and posterior doi^sal 

 nerves, in a direction similar to the fibres of this muscle, 

 which run perpendicularly to the linea alba. On the ex- 

 ternal surface of this muscle we also see the arteries which 

 supply the abdominal walls with blood and their accom- 

 panying veins. Superiorly lumbar branches, derived directly 

 from the posterior aorta, and the circumflex artery of the 

 ilium, which arises from the external iliac artery, runs 

 directly to the antero-iuferior spinous process, and then, 

 breaks up in supplying the abdominal muscles. Posteriorly 

 the epigastric is given off by arteria profunda femoris 

 below symphysis pubis, and passing over the internal sur- 

 face of the femoral artery and of the inguinal canal, runs- 

 forwards under rectus abdominis ; it sends off the external 

 fudic artery to the sheath in the male, the mammary 

 gland in the female ; in the male also the external pudic 

 artery gives off the anterior dorsal artery of the ;penis, one 

 branch of which runs forwards along the superior part of 

 the organ as far as the glans, the other backwards to anas- 

 tomose with the posterior dorsal artery from the internal 

 pudic. 



The internal thoracic artery at the ensiform cartilage 

 divides, sending one branch, the anterior abdominal, along 

 the floor of the abdomen, the other upwards along the infe- 

 rior extremities of the ribs, where it anastomoses with the 

 intercostals, and sends twigs to the abdominal walls : 

 all these arteries anastomose by their terminal twigs one 

 with the other. 



Transversalis abdominis arises from the internal sur- 

 face of the twelve posterior ribs, of their cartilages, and 

 by faschial expansion from the transverse processes of the 

 lumbar vertebrae, its fibres run to be inserted perpendicu- 

 larly into the upper surface of the ensiform cartilage and 

 the linea alba. Anteriorly inside the ribs its attachments 

 digitate with those of the diaphragm. Posteriorly its 

 fibres grow gradually more and more sparse, none being 

 found at the internal abdominal ring. By removing this 

 muscle we expose the peritoneum or serous lining mem- 

 brane of the abdomen covered in places by white fibres 



