I9& RESPIRATION. 



peculiarities in different persons and circumstances. In- 

 young children, it is effected almost entirely by the dia- 

 phragm, which being highly arched in expiration, becomes 

 flatter as it contracts, and, descending, presses on the 

 abdominal viscera, and pushes forward the front walls of 

 the abdomen. The movement 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 move- 

 ment appears less extensive in the lower, and more so in 

 the upper, part of the chest ; a mode of breathing 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 greater diversity than naturally exists in the 

 modes of inspiration. 



From the enlargement produced in inspiration, the chest 

 and lungs return in ordinary tranquil expiration, by their 

 elasticity ; the force employed by the inspiratory muscles in 

 distending the chest and overcoming the elastic resistance 

 of the lungs and chest- walls, being returned as an expira- 

 tory effort when the muscles are relaxed. This elastic 

 recoil of the rib-cartilages, but also of the lungs them- 

 selves, in consequence of the elastic tissue which they 

 contain in considerable quantity, is sufficient, in ordinary 

 quiet breathing, to expel air from the chest in the intervals 

 of inspiration, and no muscular power is required. In all . 

 voluntary expiratory efforts, however, as in speaking, 

 singing, blowing, and the like, and in many involuntary 



