120 TOPOGRAPHIC AND APPLIED ANATOMY. 



PLATE 11. 



The position of the thoracic and abdominal viscera of a boy. Anterior view. From an accurate Leipzig model 

 made from an original dissection. 



PLATE 12. 

 The position of the thoracic and abdominal viscera of a boy. Posterior view. From the model of Plate n. 



points of the costal margins to the pubic spines subdivide the mesogastric region into a central 

 umbilical region and two lateral abdominal regions; they also subdivide the hypogastric region 

 into a central pubic region and two lateral or inguinal regions. The lumbar regions are in the 

 posterior portion of the mesogastric region and extend from the spinal column to a line which 

 represents the shortest distance between the costal margin and the crest of the ilium. [This 

 manner of delimiting the abdominal regions differs from that adopetd by English writers and 

 even from other Gerrnan authors. ED.] 



The skin 0} the abdomen is comparatively thin and movable, except at the navel; it is also 

 very elastic, as is shown by the distention produced by tumors, ascites, or pregnancy. The so- 

 called stria gravidarum are not an absolute indication of a preceding pregnancy, since they may 

 be produced by any distention of the abdominal integument. The fat in the subcutaneous con- 

 nective tissue is often so pronounced that it interferes with the palpation of the internal organs 

 and is a disturbing factor in the performance of laparotomy. 



Muscles. In contrast to the thoracic wall, the greater portion of the abdominal wall is 

 composed of muscular tissue; the palpation of the abdomen is consequently of more importance 

 than the palpation of the thorax. The abdominal muscles extend between the inferior aperture 

 of the thorax, the transverse processes of the lumbar vertebras, the iliac crest, the symphysis, 

 and Poupart's ligament. The rectus abdominis muscle arises from the outer surfaces of the fifth 

 to the seventh costal cartilages and from the xiphoid process, and is inserted into and alongside 

 of the anterior surface of the symphysis. It is surrounded by a fibrous sheath which is complete 

 anteriorly, but on the posterior surface of the muscle it extends only tw r o fingerbreadths below 

 the navel (linea semicircularis Douglasi), so that the only structures beneath the muscle in this 

 situation are the thin transversalis fascia and the peritoneum. The aponeuroses of the three 

 flat abdominal muscles are united in the median line to form the linea alba, which contains few 

 blood-vessels and is consequently frequently chosen as the site of the incision for operative pro- 

 cedures upon the abdomen. Above the umbilicus, it is broader and thinner; while below, it 

 is narrower and thicker. [Below the navel, owing to the fact that the recti are more closely 

 approximated, in the lower fourth the aponeuroses all pass in front of the recti, the linea 

 alba is often scarcely apparent. ED.] The greater breadth above the navel is responsible for the 

 fact that hernias of the linea alba are more frequent above than below this location. These 

 hernias pass through the slit-like orifices which transmit the vessels from the underlying struc- 

 tures to the skin. The external oblique muscle of the abdomen is situated beneath the super- 

 ficial fascia; it arises from the outer surfaces of the seven or eight lower ribs and is inserted into 

 the linea alba, the outer lip of the iliac crest, anterior one-half, and Poupart's ligament. Under- 

 lying this muscle is the internal oblique, which arises from the lumbar fascia, from the middle 

 lip of the iliac crest [anterior two-thirds. ED.], and from Poupart's ligament, and is inserted into 

 the ends of the tenth to the twelfth ribs and into the linea alba. [By means of its aponeurosis 



