RATE OF RESPIRATION 145 



After every six to ten respiratory acts a more profound 

 (sighing) inspiration than usual is taken, the effect being a 

 more thorough changing of the pulmonary contents. Cough- 

 ing, sneezing, hiccoughing, laughing, etc., all interfere with 

 rhythmical respiration. 



Modified Respiration. In coughing and sneezing a pro- 

 found inspiration precedes a violent convulsive contraction 

 of the expiratory muscles. Sighing is an expression on the 

 part of the tissues that more oxygen is needed and that, 

 therefore, the contents of the lungs must be more completely 

 changed. Yawning is a phenomenon similar to sighing, but 

 may not represent deficient oxygenation, as when it occurs 

 from contagion. Except in the contraction of different fa- 

 cial muscles, sobbing and laughing are identical from a re- 

 spiratory standpoint; in both there is a succession of quick 

 contractions of the diaphragm. Hiccough is an involuntary 

 contraction of the diaphragm accompanied by closure of the 

 glottis. It takes place during inspiration. In hawking the 

 glottis is open and a continuous expiratory current is sent 

 through the narrowed passage between the base of the 

 tongue and the soft palate. Snoring occurs with the mouth 

 open ; the current of air throws the uvula into vibration and 

 produces the characteristic sounds. 



Sounds of Respiration. When the ear is applied to the 

 chest there is heard during inspiration a breezy expansive 

 sound of slightly increasing intensity throughout, and ceas- 

 ing abruptly at the end of the act. Immediately begins the 

 expiratory sound, very short, lower in pitch than the inspira- 

 tory, and gradually decreasing in intensity until it is lost 

 before expiration is more than one-fourth finished. When 

 listening over a large bronchus this sound is prolonged and 

 has a higher pitch than usual. Respiratory sounds are more 

 pronounced in the female than in the male chest, owing to 

 the predominance of costal breathing in the former sex. 



Rate of Respiration. The respiratory rate sustains a fair- 

 ly constant relation to the cardiac rate, the ratio being about 

 10 



