66 



ANATOMY FOR NURSES. 



[CHAP. VI, 



effected by the expansion and contraction of its lateral walls, 

 called costal respiration, and by the depression and elevation 

 of the floor of the cavity, through contraction and relaxation 



of the diaphragm, called dia- 

 phragmatic or abdominal respi- 

 ration. These two movements 

 are normally combined in the 

 act of respiration, but in dif- 

 ferent circumstances one of 

 them may be resorted to 

 more than the other. Abdom- 

 inal respiration predominates 

 in men and in children, and 

 costal respiration in women. 

 In the act of inspiration the 

 diaphragm contracts, and in 

 contracting flattens out and 

 descends, the abdominal vis- 

 cera are pressed downwards, 

 and the thorax is expanded 

 vertically. In normal and 

 quiet expiration the diminu- 

 tion of the capacity of the 

 chest is mainly due to the re- 

 turn of the walls of the chest 

 to the condition of rest, in con- 

 sequence of their own elastic 

 reaction, and of the elasticity 

 and weight of the viscera dis- 

 placed by inspiration. In more 

 forcible acts of expiration, and 

 in efforts of expulsion from 

 the thoracic and abdominal 

 cavities, all the muscles which 

 tend to depress the ribs, and 

 those which compress the ab- 

 dominal cavity, concur in pow- 

 erful action to empty the lungs, to fix the trunk, and to expel the 

 contents of the abdominal viscera. Thus the diaphragm is an 

 expulsive as well as the chief respiratory muscle of the body. 



FIG. 58. MUSCLES OF ARM. 58, biceps 



5 ( J, triceps. 



