360 



THE HUMAN BODY. 



diaphragm is dome-shaped, its concavity being turned 

 towards the abdomen. From the tendon on the crown of 

 the dome striped muscular fibres radiate, downwards and 

 outwards, to all sides; and are fixed by their inferior ends 

 "to the lower ribs, the breast-bone, and the vertebral column. 

 In expiration the lower lateral portions of the diaphragm 

 lie close against the chest-walls, no lung intervening between 

 them. In inspiration the muscular fibres, shortening, fiat- 



Fio. 109. The skeleton of the thorax 

 clavicle; d, third rib; i, glenoid fossa. 



a, gr, vertebral column ; &, first rib ; c, 



ten the dome and so enlarge the thoracic cavity at the ex- 

 pense of the abdominal; and at the same time its lateral 

 portions are pulled away from the chest-walls, leaving a 

 space into which the lower ends of the lungs expand. The 

 contraction of the diaphragm thus increases greatly the size 

 of the thorax chamber by adding to its lowest and widest 

 part. 



The Dorso- Ventral Enlargement of the Thorax. The 

 Tibs on the whole slope downwards (t, Fig. 25)* from the 

 Tertebral column to the breast-bone, the slope being most 



p.m 



