Mr. Le Gros Clark on the Mechanism of Respiration. 135 



but against the relaxed diaphragm — relaxed, that is, by the abdominal 

 muscles drawing down the lower ribs, and thus contracting the circum- 

 ference of the lower part of the chest. 



The intercostal muscles also contribute importantly to this result, as the 

 effect of their contraction is reversed, by the lower ribs being relatively 

 fixed during the action of the abdominal muscles. In this way both the 

 long diameter and circumference of the chest are abridged. 



10. The upper and lower costal movements in both sexes, when entirely 

 unfettered, are equal, in ordinary inspiration and in the uncontracted 

 chest. 



The costal movements, both upper and lower, are much greater in forced 

 inspiration in the male than in the female. 



In both, the lower costal movements are much abridged by compression 

 of the abdomen and lower part of the chest, while the upper costal move- 

 ments are exaggerated. 



The observed fact that women breathe more by the chest than by the 

 abdomen is due to artificial compression, and to the altered form of the 

 chest consequent on its early adoption. 



