AND PHYSIOLOGY. 



125 



A View of the Under Side of the Diaphragm. 1, 2, 3, The Greater Muscle of the Dia- 

 phragm inserted into the Cordiform Tendon. 4, The small triangular space behind the 

 Sternum, covered only by Serous Membrane, and through which Hernia sometimes 

 pass. 5, Ligamentum Arcuatum of the Left Side. 6, Point of Origin of the Psoas Mag- 

 nus. 7, A small Opening for the Lesser Splanchnic Nerve. 8, One of the Crura of the 

 Diaphragm. 9, Fourth Lumbar Yertebra. 10, Another Cms or portion of the Lesser 

 Muscle of the Diaphragm. 11, Hiatus Aorticus. 12, Foramen <Esophageum. 13, Fora- 

 men Quadratum. 14, Psoas Magnus Muscle. 15, Quadratus Lumborum. 



250. Intercostal Muscles —Between the ribs are placed 

 two sets of muscular fibres, an external and an internal, called 

 the Intercostal Muscles, which by their action draw the ribs 

 upwards. The fibres run in a diagonal direction from one rib 

 to another, so that the greatest length may be given for their 

 contraction without compromising too much of their power. 

 And hence we can see that while the first rib is firm and im- 

 movable, by contraction of these fibres the ribs must be raised, 

 and by their relaxation they must be depressed. The exter- 

 nal fibres run downwards and towards the middle line of the 

 abdomen, while the internal run downwards and backwards. • 



251. Abdominal Muscles— The principal muscles of the 

 abdomen are large and thin expansions of muscular fibres, 



250. Give the arrangement of fibres in the Intercostal Muscles. 251. What forms the 

 principal part of the walls of the abdomen ? 



