116 MODIFICATION OF RESPIRATION. 



2. Bending the rib cartilages, and lifting the chest. 



3. Stretching the lungs. 



ELASTIC REACTIONS OF EXPIRATION. 



1. Elastic reaction of the abdominal walls and contents. 

 . 2. Elastic reaction of the rib cartilages. 



3. Elastic reaction of the lungs. 



Thus far we have been speaking of ordinary respiration. 

 In forced respiration, as in shouting, many muscles are brought 

 into play to expel the air rapidly and forcibly. In such an 

 act as coughing there is vigorous action of the abdominal 

 muscles. 



The main part of respiration is performed by the dia- 

 phragm ; and the more common mode of respiration is there- 

 fore called abdominal, or diaphragmatic, respiration. In women 

 of the civilized races, respiration is more largely accomplished 

 by the action of the thoracic muscles, and is called thoracic, 

 or costal, respiration. In children the respiration is of the 

 abdominal type. 



Ordinary inspiration takes slightly less time than expira- 

 tion. 



The rate of respiration in the adult varies from sixteen to 

 twenty-four per minute, the average being about seventeen 

 times a minute ; about one respiration for every four heart- 

 beats. Light is favorable to respiratory activity. 



The rate is affected. by the position of the body, state of 

 activity, temperature, digestion, emotions, age, disease, etc. 



Coughing is a forcible expiration, usually directed through 

 the mouth, and for the purpose of getting rid of some foreign 

 substance, or caused by irritation. In sneezing there is first 

 a deep inspiration, and then the current of air is forced out, 

 chiefly through the nose. Sneezing may be prevented by 

 pressing firmly on the upper lip. Crying, laughing, sobbing, 



