282 
RESPIRATORY MOVEMENTS OF MAMMALS. 
movement of the diaphragm; and in the second, by that of 
the ribs. 
331. i. The diaphragm, in a state of rest or relaxation, 
forms a high arch, which rises into the interior of the chest, 
as at < 7 , fig. 163 ; but when it contracts, it becomes much 
flatter (though always retaining some degree of convexity 
upwards), and thus adds considerably to the capacity of the 
lower part of the chest. The under side of the diaphragm is 
in contact with the liver and stomach, which, to a certain 
i a c 
c a h 
Fig. 163. —Thorax of Man. 
degree, rise and fall with it. It is obvious that, when the 
diaphragm descends, these organs, with the abdominal viscera 
in general, must be pushed downwards ; and as there can be 
no yielding in that direction, the abdomen is made to bulge 
forwards when the breath is drawn-in. On the other hand, 
when the contraction of the diaphragm ceases, the abdominal 
muscles press back the contents of the abdomen, force up the 
