MECHANISM OF RESPIRATION. 



139 



rise and fall are comparatively slight, that only in deep inspira- 

 tions is the upper end of the bone raised at all, and that 

 while in the best formed chests its lower end moves some- 

 what upwards and forwards in ordinary breathing, there are 

 many chests in which there is little or no movement of the 



Fig. 78. VERTICAL TRANSVERSE SECTION OF CHEST AND STOMACH, 

 to show the arched form of a, a, the diaphragm; b, the heart; c, c, 

 lungs; d, liver; e, stomach; /, spleen; g, pancreas. The reflexions 

 of the pericardium and pleurse round the heart and lungs are 

 represented. Altered from Luschke. 



breast bone at all. The enlargement of the chest, by move- 

 ment of the ribs, in quiet breathing, is therefore principally 

 effected by raising the lateral arches or hoops formed by 

 large ribs, so as to bring them into the positions previously 

 occupied by smaller ribs above them ; and in deep inspira- 



