THE ABDOMKX. 957 



Boundaries. The all<>in> // ^ roper is divided for description into the abdominal 

 ii'dll or boundaries and the abdominal cavity and contents. The boundaries are 

 a /"/. a floor, and the trail, which includes an antero-lateral and a posterior por- 

 tion ; the former is soft and contractile, muscular on the sides, fibrous and 

 aponeurotic in the centre ; the posterior wall is partly osseous, ligamentous and 

 muscular. 



Several facts depend on the character of the antero-lateral wall. It does not 

 offer to the viscera and great vessels a passive protection as does the skull to its 

 contents, but allows a mutual reaction which is of the greatest importance. It 

 yields lightly to every pressure and corresponds to the changing volume of the 

 intestines and to the changes of position and form of the viscera. Atmospheric 

 pressure acts on every side, but this is overlooked when the many muscles are 

 considered which exert a constant tension. The relations of each organ to its 

 neighbor are modified by this tension, and soft organs like the liver, pancreas, or 

 spleen are moulded by it and show the imprint of nearly every viscus that touches 

 them. The tension is seen in cases of penetrating wounds, where the movable 

 intestines tend to flow toward the spot of least resistance and are replaced or 

 restrained with difficulty. The same pressure helps to develop hernife and forces 

 the portal circulation through the liver. 



The shape of the soft antero-lateral wall depends upon the degree of disten- 

 tion of the alimentary canal, the size of the parenchymatous organs, and espe- 

 cially upon the deposit of fat in the subcutaneous tissue, in the peritoneal folds, 

 and in the great omentum. All gradations occur between the great fat belly 

 which depends over the thighs and the concave trough-like one of a thin person. 

 The pliability and thinness of the wall allow palpation to be of more value here 

 in diagnosis than percussion. 



The component parts of the walls have already been discussed. A brief 

 review is here added (Fig. 575). 



In the antero-lateral wall from without inward are found in order : 



1. Skin. 



2. Superficial fascia, two layers. 



3. Cellular tissue covering the External oblique muscle, and intercolumnar 

 fascia from the external abdominal ring. 



4. Muscles of the wall. Broad muscles the External oblique and aponeur- 

 osis. the Internal oblique and aponeurosis, the Transversalis and aponeurosis. 

 Longitudinal muscles the Rectus and Pyramidalis. 



5. Fascia transversalis. 



6. Subperitoneal cellular tissue. 



7. Peritoneum. 



In this wall several regions are described : the inguinal, inguino-femoral, and 

 umbilical. 



The arteries of the antero-lateral wall are superficial and deep ; the super- 

 ficial epigastric and superficial circumflex-iliac from the femoral, the lower two 

 intercostals from the thoracic aorta, the lumbar from the abdominal aorta, and 

 ilio-lumbar from the internal iliac. Above are the superior epigastric and mus- 

 culo-phrenic from the internal mammary all forming the superficial set. Below 

 are the deep circumflex-iliac and deep epigastric (inferior epigastric) from the 

 external iliac. The latter is the most important and gives off the cremasteric 

 artery, pubic and muscular branches. There is an anastomosis between the two 

 lower epigastrics and between the deep epigastric and the internal mammary. 



The veins are also divided into a superficial and deep set. Superficial are the 

 superficial epigastric and superficial circumflex-iliac and another which passes 

 subcutaneously along the side of the thorax, connecting above with the axillary 

 vein and emptying below into either the superficial epigastric vein or into the 

 femoral through the saphenous opening. It is dignified by the name l^cna 

 thoracico-epi<!<ixtr<<-'i //#;// t>-;-niriit>ntox<i ( Braune). The deep veins accompany 

 their corresponding arteries and are usually double. The superficial veins do not 



