392 RESPIRATION. 



The relations of the respiratory acts to the pulse are quite 

 constant in health. It has been shown by Hutchinsoii that 

 the proportion in the great majority of instances is one re- 

 spiratory act to every four pulsations of the heart. The same 

 proportion generally obtains when the pulse is accelerated in 

 disease, except when the pulmonary organs are involved. 



Age has an influence on the frequency of the respiratory 

 acts, corresponding with what we have already noted with 

 regard to the pulsations of the heart. 



Quetelet gives the following as the results of observations 

 on 300 males : 



44 respirations per minute soon after birth ; 



26, at the age of five years ; 



20, at the age of fifteen to twenty years ; 



19, at the age of twenty to twenty-five years ; 



16, about the thirtieth year ; 



18, from thirty to fifty years. 



The influence of sex is not marked in very young chil- 

 dren. The same observer noted 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. 1 



The various physiological conditions which have been 

 noted as affecting the pulse have a corresponding influence 

 on respiration. In sleep the number of respiratory acts is 

 diminished about twenty per cent (Quetelet). Muscular ef- 

 fort accelerates the respiration pari passu with the move- 

 ments of the heart. 



Relations of Inspiration and Expiration to each other. 

 The Respiratory Sounds. In ordinary respiration, inspira- 

 tion is produced by the action of muscles, and expiration, in 

 greatest part, by the passive reaction of the elastic walls of 

 the thorax and the lungs. The inspiratory and expiratory 

 acts do not immediately follow each other. Commencing 



1 MILNE-EDWARDS, Lefons de Physiologic, tome ii., pp. 482, 483. 



