RESPIRATION 



173 



disadvantage. (3) The lateral costal. Here the abdominal 

 muscles act at the same time as the ribs and the diaphragm. 

 This form of breathing produces the highest pressures 

 on the contents of the abdominal cavity and maintains the 

 tone of the abdominal walls without diminishing the effi- 

 ciency of the oxygenation of the blood. It also forces the 



FIG. 80. Action of the diaphragm in abdominal and in lateral 

 costal breathing 



Solid lines represent position of body wall, diaphragm, and ribs during expira- 

 tion; dotted lines, the same during inspiration. The left-hand figure represents 

 abdominal breathing, the diaphragm becoming more convex, displacing down- 

 ward the abdominal viscera and forcing outward the abdominal body wall. In 

 the lateral costal type the diaphragm raises the lower ribs, and the abdominal 

 walls may actually move inward, owing to the contraction of their muscles 



use of the upper ribs to a much greater extent than does 

 the predominantly abdominal type of breathing (Fig. 80). 



It is seldom that one or another of these types is used 

 in its entirety, and the advantages of one form over another 

 are often greatly exaggerated. The following statements 

 may, however, be taken as summing up the essential 

 practical points. 



