148 ANATOMY AND PHYSIOLOGY FOR NURSES 



tion, and requires accordingly to be as rapidly expelled 

 and replaced by a fresh supply. The exchange or reno- 

 vation of the air is effected by alternate movements of the 

 chest of expansion and collapse, which follow each other 

 in regular succession, and which are known as the move- 

 ments of inspiration and expiration. 



In inspiration the lungs fill with air, in expiration the 

 air is expelled. The movements of respiration are in- 

 voluntary in character, and even their acceleration or 

 diminution is regulated by influences beyond our control. 

 We may for a short time control these movements, but 

 that for a limited time only, as the nervous impulse be- 



FlG. 72. Diagrammatic representation of the termination of a bronchial 

 tube in a group of infundibula : B, Bronchial tube ; LB, bronchiole : A, 

 atrium ; /, infundibulum ; C, alveoli (Nancrede). 



comes so very active that we are forced to breathe. Then 

 again, if we try to breathe more rapidly than the normal 

 respirations, we become fatigued and return to the normal 

 standard. Respiration is, therefore, automatic in charac- 

 ter, as may be noticed in persons during sleep; it is like 

 the heart in that it requires no effort upon our part to 

 maintain its action. 



The respiratory movements vary according to age in 

 sleeping and exercise. There are four pulsations of the 

 heart to one respiratory act. 



The air which is drawn into the lungs in respiration is 



