AUSCULTATION. 



241 



The degree of resonance on percussion is very 

 considerably modified in different persons by the 

 form and bodily condition of the patient. The 

 chest of a thin, spare person, gives a much louder 

 and clearer sound than one which is well clothed 

 with fat and flesh. All this is easily taken into 

 consideration by the physician, so that he is in 

 little danger of mistaking an accumulation without 

 the cfrest for disease within. A comparison between 

 the two sides of the chest gives additional security 

 against such a mistake. In some parts, it is true, 

 the organs are different in the two sides ; but to a 

 considerable extent they correspond. It is also 

 true, that the same state of disease may exist in 

 the corresponding parts, so as to obscure the results 

 of a comparison between them. But this is ex- 

 tremely rare. . In general there is a marked differ- 

 ence in the sound of the two sides in most cases of 

 decided disease. To take advantage of this com- 

 parison, it is of course necessary, that the practi- 

 tioner be accurate in his knowledge of the anatomy 

 of the parts, or he may confound the flatness pro- 

 duced by striking upon a solid organ for that of 

 diseased structure. 



The practice of auscultation is founded upon 

 principles of physical science equally well esta- 

 blished. Sounds, which are caused by certain ac- 

 tions within the cavities of the body, are trans- 

 mitted through the walls of the cavity, and are 

 perceived when the ear is applied closely to the 

 surface, or through the intervention of a proper 

 instrument. These sounds are always alike under 

 like circumstances, and are changed when the cir- 

 cumstances which caused them are changed. Hence 

 the physician, if he render his ear familiar with the 

 sounds caused by the internal actions of the body 

 in a healthy state, will readily perceive a variation, 

 when the part is diseased. What disease is indi- 

 tated by any particular unnatural sound, he can 

 learn only from repeated and extensive observa- 

 tions. But that there is a deviation from the 

 natural state, he will perceive at once; and the 

 accumulated observations of all the physicians, 

 whose attention has been directed to the subject, 

 have now gone far to explain most of the deviations 

 which have been noticed. 



These principles are chiefly available for practical 

 purposes in reference to the actions of the lungs 

 and the heart. The air in passing through the 

 windpipe gives rise to a certain sound, which in 

 health is always nearly the same. This sound is 

 modified in the smaller tubes (the bronchia) into 

 which the windpipe divides, and again still more 

 decidedly in the little air vesicles in which the 

 bronchia terminate, and which occupy every part of 

 the lungs. These several sounds are readily per- 

 ceived and easily distinguished by a practised ear, 

 applied to the corresponding part of the chest and 

 neck. Hence we have tracheal, bronchial, and 

 vesicular respiration ; and if these are heard only 

 in their appropriate places, and in a right degree of 

 force, they indicate a healthy state of the parts. 



When a portion of the lung is diseased, the cur- 

 rent of air in that part is either obstructed or its 

 natural force changed, and of course the sound is 

 modified. Hence, by applying the ear extensively 

 over the chest, we are unable to detect the exis- 

 tence, and the precise seat, and generally the na- 

 ture, of the disease. In inflammation of the lungs, 

 the air cells are for the time obliterated in the part 

 affected. As there are no vesicles for the air to 

 enter, there is no vesicular respiration. But we 



VII. 



have, what would not at first view be anticipated, 

 bronchial respiration in its stead. In the healthy 

 condition of the lungs, the porous character of the 

 vesicular structure renders it a bad conductor of 

 sound, so that the sound caused by the air in the 

 bronchial tubes is not transmitted through them. 

 But when they are consolidated by disease, they 

 become good conductors of sound ; and, at the 

 same time, the morbid condition of the parts gives 

 a greater degree of intensity to the sound itself. 



Bronchial respiration, then, heard in the place of 

 vesicular, always indicates inflammation? That 

 would be a simplicity in the art of distinguishing 

 diseases, which nature does not tolerate. But it 

 always indicates a consolidation of the lung from 

 some cause, and inflammation is one of the most 

 frequent of the causes. Another, and unhappily a 

 frequent cause, is the deposition of tubercles, in 

 incipient consumption. As in regard to percussion, 

 so in reference to auscultation, there are means of 

 distinguishing between the several morbid affec- 

 tions, which give rise to phenomena in many re- 

 spects similar. These it is the business of the 

 physician to study, and they often exercise his in- 

 genuity and industry not a little. But it would 

 lead us too far to attempt to explain them here. 



There are other morbid sounds in the respiration, 

 besides those which arise from what we may call 

 the misplacement of such as are healthy. When 

 the membrane which lines the air passages is in- 

 flamed, as in common cold or catarrh, its surface is 

 at first unnaturally dry ; and in that state the cur- 

 rent of air through the tubes gives rise to various 

 sounds more or less musical, which are the different 

 modifications of the sonorous rdle.* At a later 

 period the membrane becomes more than naturally 

 moist, and the passages are crowded, and more or 

 less obstructed, by an adhesive fluid. In this state, 

 if the ear is applied to the chest, the air is heard 

 bubbling through the mucus, and this is the mucous 

 rdle. Inflammation of the substance of the lung, 

 in its earlier stage, before the air vesicles are 

 obliterated, is accompanied by a still different rdle, 

 the crepitous. In the advanced stage of consump- 

 tion, a cavity, sometimes more than one, is formed 

 in the lungs, at first filled with purulent matter, 

 which is afterwards discharged through an opening 

 into a bronchial tube. The air as it rushes into, 

 and out of, this cavity, in every respiration gives 

 rise to a peculiar hollow sound, which is the ca- 

 vernous rdle. If the cavity is very large, and the 

 opening into it from the bronchia small, the sound 

 resembles that caused by blowing into the mouth 

 of an empty bottle (amphoric resonance). The 

 same sound is produced when air escapes into the 

 cavity of the chest, compressing the lung; which 

 is sometimes the result of an accidental injury, and 

 sometimes of ulceration. 



The sounds of the voice give still farther aid in 

 detecting and distinguishing the diseases of the 

 lungs. In the healthy state of those organs, no 

 peculiar sensation is communicated to the ear, un- 

 less it be applied over the windpipe, or over the 

 larger bronchia at the root of the lungs. But 



* There i* a jrood deal of difference of opinion as to the best 

 term to dednm those morbid sound*. Some writers use the 

 Kn;.'lis1i word i-attlf, and others the Latin rhonchtu. \Vepre- 

 CIT to adopt the French raff, used by Laonnoo. Where the 

 thin? 1o be expressed is new, it is bettor to adopt a new word, 

 than to assign a new meaning to a word already in common 

 use. As no new Knglish word has been proposed we can only 

 do this by borrowing from a foreign language ; and the French 

 term was tirst introduced, and is more extensively used, and 

 more atreeable to the car than the Latin. 



