134 KESPIRATION. 



piration follows. This is also tubular in quality ; it soon attains its maximum of intensity, 

 but, unlike the sound of inspiration, gradually dies away and is lost imperceptibly. It is 

 seen that these phenomena correspond with the nature of the two acts of respiration. 



Sounds approximating in character to the foregoing are heard over the bronchial 

 tubes before they penetrate the lungs. 



Over the substance of the lungs, a sound may be heard entirely different in its char- 

 acter from that heard over the larynx, trachea, or bronchial tubes. In inspiration, the 

 sound is much less intense than over the trachea and has a breezy, expansive, or what 

 is called in auscultation a vesicular character. It is much lower in pitch than the trachea! 

 sound. It is continuous and rather increases in intensity from its commencement to its 

 termination, ending abruptly, like the tracheal inspiratory sound. The sound is produced 

 in part by the movement of air in the small bronchial tubes, but chiefly by the expansion 

 of the innumerable air-cells of the lungs. It is followed, without an interval, by the sound 

 of expiration, which is shorter, one-fifth to one-fourth as long, lower in pitch, and very 

 much less intense. A sound is not always heard in expiration. 



The variations in the intensity of the respiratory sounds in different individuals are 

 very considerable. As a rule they are more intense in young persons ; which has given 

 rise to the term puerile respiration, when the sounds are exaggerated in parts of the lung, 

 in certain cases of disease. The sounds are generally more intense in females than in 

 males, particularly in the upper regions of the thorax. 



It is difficult by any description or comparison to convey an accurate idea of the 

 character of the sounds heard over the lungs and air-passages, and it is superfluous to 

 make the attempt, when they can be so easily studied in the living subject. 



Coughing, Sneezing, Sighing, Yawning, Laughing, Sobbing, and Hiccough. These 

 peculiar acts demand a few words of explanation. Coughing and sneezing are gen- 

 erally involuntary acts, produced by irritation in the air-tubes or nasal passages, al- 

 though coughing is often voluntary. In both of these acts, there is first a deep in- 

 spiration, followed by a convulsive action of the expiratory muscles, by which the 

 air is violently expelled with a characteristic sound, in the one case by the mouth, 

 and in the other by the mouth and nares. Foreign bodies lodged in the air-passages 

 are frequently expelled in violent fits of coughing. In hypersecretion of the bron- 

 chial mucous membrane, the accumulated mucus is carried by the act of coughing 

 either to the mouth or well into the larynx, whence it is expelled by the act of ex- 

 pectoration. When either of these acts is the result of irritation from a foreign sub- 

 stance or secretions, it may be modified or partly smothered by the will, but is not com- 

 pletely under control. The exquisite sensibility of the mucous membrane at the summit 

 of the air-passages, under most circumstances, protects them from the entrance of foreign 

 matters, both liquid and solid ; for the slightest impression received by the membrane 

 gives rise to a violent and involuntary cough, by which the offending matter is removed. 

 The glottis is also spasmodically contracted. 



In sighing, a prolonged and deep inspiration is followed by a rapid and generally an 

 audible expiration. This occurs, as a general rule, once in from five to eight respiratory 

 acts, for the purpose of changing the air in the lungs more completely, and it is due to an 

 exaggeration of the cause which gives rise to the ordinary acts of respiration. When due 

 to depressing emotions, it has the same cause; for, at such times, respiration is less 

 effectually performed. Yawning is an analogous process, but differs from sighing in the 

 fact that it is involuntary and cannot be produced by an effort of the will. It is charac- 

 terized by a wide opening of the mouth and a very profound inspiration. Yawning is 

 generally assumed to be an evidence of fatigue, but it often occurs from a sort of con- 

 tagion. When not the result of imitation, it has the same exciting cause as sighing, viz., 

 deficient oxygenation of the blood, and it is followed by a sense of satisfaction, which shows 

 that it meets some decided want on the part of the system. 



