108 RESPIRATION 



heart. The same proportion usually obtains when the pulse is accel- 

 erated in disease, except when the pulmonary organs are involved. 



Age has an influence on the frequency of the respiratory acts, corre- 

 sponding with what has already been noted in regard to the pulsations of 

 the heart. 



The following are the results of observations on three hundred males 

 (Quetelet) : 



Forty-four respirations per minute, soon after birth ; 



Twenty-six, at the age of five years ; 



Twenty, between fifteen and twenty years ; 



Nineteen, between twenty and twenty-five years ; 



Sixteen, about the thirtieth year ; 



Eighteen, between thirty and fifty years. 



The influence of sex is not marked in very young children. There 

 is no difference between males and females at birth ; but in young 

 women, the respirations are a little less frequent than in young men of 

 the same age. 



.- The various physiological conditions which have been noted as affect- 

 ing the pulse have a corresponding influence on respiration. In sleep 

 the number of respiratory acts is diminished by about twenty per cent 

 (Quetelet). Muscular effort accelerates the respiratory movements pari 

 passu with the movements of the heart. 



Relations of Inspiration and Expiration to each other, Respiratory 

 Sounds. In ordinary respiration, inspiration is produced by the action 

 of muscles, and expiration, by the passive reaction of the lungs and of 

 the elastic walls of the thorax. The inspiratory and expiratory acts do 

 not follow each other immediately. Beginning with inspiration, it is 

 found that this act maintains about the same intensity throughout. There 

 is then a very brief interval, when expiration follows, which has its maxi- 

 mum of intensity at the beginning of the act and gradually dies away. 

 Between the acts of expiration and inspiration is an interval somewhat 

 longer than the interval between inspiration and expiration. 



The duration of expiration usually is a little longer than that of 

 inspiration, although the two acts may be nearly, or in some instances, 

 quite equal. After five to eight ordinary respiratory acts, an effort 

 commonly is made which is rather more profound than usual, by which 

 the air in the lungs is more thoroughly changed. Temporary arrest of 

 the acts of respiration in violent muscular efforts, in straining, in partu- 

 rition etc., is sufficiently familiar. 



Ordinarily respiration is not accompanied with any sound that can be 

 heard without applying the ear directly, or by the intervention of a stetho- 

 scope, to the chest, except when the mouth is closed and breathing is 



