362 THE HUMAN BODY. 



the upper ribs. The external intercostals (Fig. 112, A) lie 

 between the ribs and extend from the vertebral column to the 

 costal cartilages; their fibres slope downwards and forwards. 

 During an inspiration the scalenes contract and fix the 

 upper ribs firmly; then the external intercostals shorten 

 and each raises the rib below it. The muscle, in fact, 

 ; tends to pull together the pair of ribs between which it 

 lies, but as the upper one of these is held tight by the 



FIG. 112. Portions of four ribs of a dog with the muscles between them, a, a, 

 ventral ends of the ribs, joining at c the rib cartilages, 6, \vhich are fixed to 

 cartilaginous portions, d, of the sternum. A, external intercostal muscle, ceas- 

 ing between the rib cartilages, where the internal intercostal, B, is seen. Between 

 the middle two ribs the external intercostal muscle has been dissected away, so 

 as to display the internal which was covered by it. 



scalenes and other muscles above, the result is that the lower 

 rib is pulled up, and not the upper down. In this way the 

 lower ribs are raised much more than the upper, for the 

 whole external intercostal muscles on one side may be re- 

 garded as one great muscle with many bellies, each belly 

 separated from the next by a tendon, represented by the 

 rib. When the whole muscular sheet is fixed above and 



