THORAX 



The fibres of the diaphragm, in the region in question, correspond 

 somewhat in their direction with those of the internal intercostal 

 muscles, and it is no uncommon occurrence for the student to 

 remove them, and thus expose the peritoneum, under the im- 

 pression that he has laid bare the pleura. When the dissection 

 of the lower intercostal spaces is properly executed a strong fascia 

 will be exposed as the internal intercostal muscles are removed. 



M. sternohyoideus 

 M. sternothyreoideus 



M. transvcrsus thoraci 



Intercostal nerve 

 and artery 



Internal mammary 

 artery 



Sternal glands 



M. transversus 

 horacis 

 Musculo- 

 'phrenic artery 



Superior epigastric 

 artery 



M. transversus 

 abdominis 



FlG. 4. Dissection of the posterior surface of the Anterior Wall of the Thorax. 



It passes from the surface of the diaphragm to the costal pleura 

 and holds the latter in position. Preserve it for further 

 examination. 



Arteria Mammaria Interna. Each internal mammary 

 artery arises, in the root of the neck, from the first part of 

 the corresponding subclavian artery. It enters the thorax by 

 passing downwards, posterior to the sternal end of the clavicle 

 and the cartilage of the first rib, and it descends to the interval 



