RESPIRATION 37 



the powerful and elastic muscles of the abdominal wall, 

 begin to press on the diaphragm and force it to resume 

 its dome shape. The ribs drop back into their position 

 of rest, the elastic lungs contract and drive out the air 

 and thorax, diaphragm and lungs are ready to repeat 

 the act of inspiration. The descent of the diaphragm 

 pushes the abdominal viscera downwards and forward 

 and this movement communicated to the abdominal 

 wall gives its name to this type of breathing, abdominal, 

 which is most noticed in children. When the lower ribs 

 only move the type is said to be inferior costal; when 

 the clavicles and upper ribs move the type is superior 

 costal. The latter is characteristic of civilized women 

 and is a possible provision for pregnancy, though many 

 observations indicate improper dress as a cause of this 

 type of inspiration. 



In forced inspiration, as in asthma, other muscles are 

 brought into play. The same is true of forced expi- 

 ration where the abdominal muscles play a large part. 



Respiratory Cycle. This consists of two parts, the in- 

 take of air, inspiration, and the output or expiration. 

 Inspiration takes a slightly shorter time than expiration, 

 the average difference being the proportion of five to 

 six; though in children, women, and the aged the pro- 

 portion may be six to eight or even nine. There is a 

 slight pause after expiration. 



Respiratory Sounds. If the ear be applied to the 

 chest during inspiration a soft murmur, like the rust- 

 ling of leaves in a gentle wind, is heard, followed, dur- 

 ing expiration, by a similar sound during a shorter 

 lime. Note the apparent contradiction: The time of 

 inspiration is shorter than that of expiration, but the in- 

 spiratory sound lasts three times as long as the expir- 

 atory. Both sounds seem to be caused by the friction of 



