650 PHYSIOLOGY OF RESPIRATION. 



The inspiration in man is made by the diaphragm alone or by the 

 diaphragm together with some action of the levatores costarum and 

 the external intercostals. At the end of the inspiration the ribs and 

 diaphragm are brought back to the normal position by purely 

 physical forces, the elasticity of the distended abdominal wall, 

 the elasticity of the expanded lungs, the weight and torsion of 

 the ribs, etc. As soon as the breathing movements become at all 

 forced the action of the above-named inspiratory muscles is in- 

 creased in intensity, and the other inspiratory muscles, all elevators 

 of the ribs, come into play. Quiet breathing in man at least is 

 mainly diaphragmatic or abdominal, while dyspneic breathing is 

 characterized by a greater action of the elevators of the ribs. 

 When dyspnea reaches a certain stage the expiration also becomes 

 active or forced. The expiratory act is hastened by a contraction 

 of the abdominal muscles or of the depressors of the ribs, and 

 indeed the action of these muscles may compress the chest beyond 

 its normal position, so that the expiration is followed by a passive 

 inspiration which brings the chest to its normal position before the 

 next active inspiration begins. 



Costal and Abdominal Types of Respiration. These two 

 types of respiration are based upon the character of the inspiratory 

 movement. An inspiration in which the movement of the abdomen, 

 due to contraction of the diaphragm, is the chief or only feature 

 belongs to the abdominal type. An inspiration in which the eleva- 

 tion of the ribs is a noticeable factor belongs to the costal type. 

 Hutchinson, who introduced this nomenclature,* laid emphasis 

 chiefly upon the order of the movements. In the abdominal 

 type the abdomen bulges outward first, and this is followed by 

 a movement of the thorax; the movement spreads from the 

 abdomen to the thorax, and, " like a wave, is lost over the thoracic 

 region." In costal breathing the upper ribs move first and the 

 abdomen second. The terms are meant to apply chiefly to human 

 respiration and have aroused interest in connection with the 

 fact that in quiet breathing in the erect posture the respiration 

 of man belongs to the abdominal type and that of woman to the 

 costal type. It has been a question whether this difference is a 

 genuine sexual distinction or depends simply upon differences 

 in dress. Hutchinson inclined to the view that it forms what we 

 should call a secondary sexual characteristic, and that its physio- 

 logical value for woman lies in the fact that provision is thus made, 

 as it were, against the period of pregnancy. He states that in 

 twenty-four young girls examined between the ages of eleven and 

 fourteen the costal type was present, although none of them had 



* See Hutchinson, article on "Thorax," Todd 's " Cyclopaedia of Anat- 

 omy and Physiology, " 1849. 



