THE DIAPHRAGM. 



243 



the dome, striped muscular fibres radiate, downwards and 

 outwards, in all directions, and are fixed by their inferior 

 ends to the lower ribs, the breast-bone, and the vertebral 

 column. In inspiration (drawing a breath) the muscular 



FIG. 69. The lower half of the thorax, with four lumbar vertebrae, showing 

 the diaphragm from above. 1, 2, 3, central tendon; 4, 5, muscular part. 



fibres, shortening, flatten the dome and so enlarge the 

 thoracic cavity at the expense of the abdominal. The con- 

 traction of the diaphragm thus greatly increases the size of 

 the thorax chamber by adding to its lowest and widest 

 part. 



What happens to it during inspiration? What results? 



