THE THORAX AS A WHOLE. 



It).' 



back in the median line is least at the top. It increases at once, owing to the back- 

 ward bend of the spine and the forward slant of the sternum, reaching the maxi- 

 mum at about the middle of the thorax. It decreases slightly below, owing to the 

 forward sweep of the spine, but the position of the lower end of the sternum is so 

 uncertain that this is very variable. The breadth of the thorax increases very 

 rapidly, reaching nearly the maximum where the third rib crosses the axillary line. 

 Below this it increases a little, being greatest where the fifth rib crosses the same 



Fig. 187 



The bony thorax, lateral view. 



line. It then continues very nearly the same with some slight diminution below. 

 The greatest length of the thoracic framework is in the axillary line, the lowest 

 point being the cartilage of the tenth or eleventh rib, which in the male may nearly 

 reach the crest of the ilium. The downward slant of the ribs and the rise of most of 

 the cartilages make the study of horizontal sections at first very confusing. The 

 relations at certain levels must be somewhat conventional, for the variations are very 

 great, depending on figure, age, health, position, and the stage of the respiratory 

 movements. Two levels must be taken as standards, subject to these corrections. 



