. Human physiology : designed for colleges and the higher classes in schools, and for general reading. a-phragm contract, the arch will be flattened, and thus the roomin the chest will be enlarged. To occupy this new room thusmade, the air rushes in through the windpipe. This is inspira-tion. In expiration, the reverse movement takes place—thearch of the diaphragm rises, and, compressing the lungs, forcesthe air out of them through the trachea. In inspiration, asthe diaphragm is flattened, it pushes down before it thestomach, liver, &c, and hence the pressing out of the abdomen,which is so sen
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. a-phragm contract, the arch will be flattened, and thus the roomin the chest will be enlarged. To occupy this new room thusmade, the air rushes in through the windpipe. This is inspira-tion. In expiration, the reverse movement takes place—thearch of the diaphragm rises, and, compressing the lungs, forcesthe air out of them through the trachea. In inspiration, asthe diaphragm is flattened, it pushes down before it thestomach, liver, &c, and hence the pressing out of the abdomen,which is so sensibly felt, if the hand be placed upon it duringthe act of inspiration. In expiration, on the other hand, the HESPIRATION. 91 In expiration little muscular action. Elasticity the chief agent. abdomen retreats inward. These two opposite states of thearch of the diaphragm, and of the walls of the abdomen, arerepresented in Fig. 39. It is a side view, the ribs being cutaway. C o is the cavity of the chest, and C a, the cavity ofthe abdomen. The diaphragm and the abdomen are represented FIG. View. as they are in expiration. The dotted line marks the flatteningof the arch of the diaphragm, and the projection of the ab-domen, as they occur in inspiration. It is supposed that inordinary expiration, there is little, if any, muscular action—that, as the diaphragm, which in inspiration pushed down thestomach and liver, and thus thrust out the walls of the ab-domen, ceases to contract and relaxes, the mere elasticity ofthe parts below, and especially of the abdominal walls, restoresthe former condition of things, and so the diaphragm is car-ried upward, and expiration results. When, however, the ex- 92 HUMAN PHYSIOLOGY. Other muscles, besides the diaphragm, act in inspiration. piration is at all forcible, it is produced in part by the actionof the muscles of the abdomen and some of the muscles aboutthe chest. 136. While this dome-shaped muscle, the diaphragm, is th
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