RESPIRATORY MOVEMENTS. 163 



accomplished also by a raising of the anterior extremities of 

 the rib cartilages, which of course, in any movement, carry 

 the sternum with them. The differences in shape and direc- 



FIG. G2. 



tion of the upper and lower true ribs, and the more acute 

 angles formed by the junction of the latter with their carti- 

 lages, make the effect much greater at the lower than at the 

 upper part of the chest. 



The expansion of the chest in inspiration presents some pe- 

 culiarities in different persons and circumstances. In young 

 children, it is effected almost entirely by the diaphragm, which 

 being highly arched in expiration, becomes flatter as it con- 

 tracts, and, descending, presses on the abdominal viscera, and 

 pushes forward the front walls of the abdomen. The move- 

 ment of the abdominal walls being here more manifest than 

 that of any other part, it is usual to call this the abdominal 

 mode or type of respiration. In adult men, together with the 

 descent of the diaphragm, and the pushing forward of the 

 front wall of the abdomen, the lower part of the chest and 

 the sternum are subject to a wide movement in inspiration. 

 In women, the movement appears less extensive in the lower, 

 and more so in the upper, part of the chest ; a mode of breath- 

 ing to which a greater mobility of the first rib is adapted, and 

 which may have for its object the provision of sufficient space 

 for respiration when the lower part of the chest is encroached 

 upon by the pregnant uterus. MM. Beau and Maissiat call 

 the former the inferior costal, and the latter the superior costal, 

 type of respiration ; but the annexed diagrams will explain 

 the difference better than the names will, for these imply a 



