CHAPTER VIII. 

 DISSECTION OF THE THORAX. 



SECTION I. 



Clean walls 

 of muscles. 



Preserve 

 nerves, 



Termination 

 of the 



costal 

 cartilages. 



Form in 

 general ; 



on a cross 

 section. 



THE WALLS OF THE THORAX. 



Dissection. The dissection of the thorax will be commenced 

 on the fourteenth day of the dissection of the body, after the removal 

 of the upper limbs. 



In the first place the sternum, ribs and costal cartilages with the 

 intervening structures, will be carefully cleaned, so that the walls of 

 the chest may be examined, but the lateral and anterior branches 

 of the intercostal nerves issuing between the ribs and cartilages 

 should be carefully preserved. The portions of the pectoralis 

 major and minor, serratus magnus, rectus abdominus, and the ex- 

 ternal and internal oblique muscles of the abdomen, will be taken 

 away, at the same time noting again the extent of their attachments ; 

 the insertion of the scalenus posticus will also be cleaned off the 

 second rib. The origin of the sub-clavicus from the first costal 

 cartilage need not be removed. Finally, by arrangement with 

 the dissectors of the abdomen and head and neck, the body will be 

 turned on to either side for a few minutes to complete the cleaning 

 of the ribs and intercostal muscles as far back as the transverse 

 processes of the vertebrae. 



THE CHEST WALL. The costal cartilages will now be clearly 

 seen ; the upper seven ribs join the sternum, the sixth and 

 seventh being close together at the lower end of the gladiolus, and 

 the eighth, ninth and tenth cartilages terminate by articulation 

 with the lower border of the cartilage above. Some distance from 

 their anterior ends, the seventh, eighth, ninth and tenth cartilages 

 will be observed to send up a short process to articulate with 

 a similar one passing downwards from the cartilage above. The 

 extremity of the eleventh rib cartilage is free, and commonly 

 forms the lowest point of the chest wall. The twelfth rib is often 

 not more than two inches or so in length. 



Form. The form of the chest is irregularly conical, with the 

 apex above and the base below ; and it may appear afterwards, 

 should the student find the lungs collapsed, that it is only partly 

 filled by the contained viscera, but during life the whole of the space 

 is occupied by the expanded lungs. It is flattened on the sides, and on 



