Abdomen. 173 



cavity is towards the pubes. The arrangement of these 

 muscles and their aponeuroses in the inguinal region will 

 be discussed under the subject of hernia. 



4. Nerves of the Abdominal Muscles. The 



anterior and lateral muscles of the abdomen are supplied 

 by the lower intercostals the internal oblique and the 

 transversalis, however, receiving, in addition, branches 

 from the ilio-hypogastric and the ilio-inguinal nerves. 

 The quadratus is ennervated by the last dorsal and the an- 

 terior branches of the lumbar nerves ; the psoas, by the an- 

 terior lumbar nerves, while the iliacus is supplied by the 

 anterior crural. In dealing with the upper extremity, we 

 drew attention to the fact that the same nerve that sup- 

 plies the shoulder joint, supplies, also, the chief muscle 

 controlling that joint and the over-lying skin as well ; or, 

 that, as in the case of the sterno-clavicular articulation, the 

 skin over the joint, as well as the chief muscles acting on 

 it, are supplied by the same nerves that supply the joint ; 

 so, in the abdomen, we have an arrangement somewhat 

 similar, viz., the intercostal nerves supply the integument, 

 as well as the muscles that protect the abdominal viscera, 

 and are, at the same time, intimately connected with the 

 nervous supply for these viscera. The connection of the 

 intercostal nerves with the abdominal organs is by means 

 of the splanchnic nerves, and the relationship may be ex- 

 plained thus : The splanchnics arise from the lower thor- 

 acic sympathetic ganglia, and communicate by means of the 

 rami communicantes with the intercostals which supply 

 the abdominal muscles, but the splanchnics are the chief 

 afferent branches to the solar plexus, and this plexus, by 

 means of its numerous branches, controls all the abdomi- 

 nal organs, hence, as can be readily seen, there is an 

 intimate nervous relationship between these organs and 

 their protectors, i.e., the abdominal muscles. The prac- 



