A manual of auscultation and percussion, embracing the physical diagnosis of diseases of the lungs and heart, and of thoracic aneurysm and of other parts

Front matter

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Preface To Sixth Edition

By permission of the son of the late author, the editor is privileged to present this invaluable "Manual " again to the medical student and practitioner.

It is fitting that the final form of a work which went through four editions under the direct revising hand of one of the masters of the science of physical diagnosis should be retained. The principles, the method, the limitations, the practical conclusions of physical examination of the thoracic viscera have never been more clearly nor more effectively described in English. The field of theory, -the countless variations in method, the rarities of pathological and clinical experience must still be studied in the great works on diagnosis, to which we must turn for exhaustive discussions. The particular need which this book was intended to fill, and which it is expected that it will again fill, is the demand of the student and of many a graduate in medicine for simplicity, directness, exactness, and authority, in dealing with physical signs in health and disease.

The need of examination of the abdominal viscera and of the nervous system, carried out as carefully as the usual examination of the heart and lungs, excuses the addition of the two chapters dealing with these subjects.

IV PREFACE

The advantage to be gained in difficult cases, and the accuracy and confirmation to be had in all cases, by the use of various accessory mechanical methods of examination, justifies reference to the principles and methods of these procedures.

For encouragement and assistance in the preparation of this edition the editor is indebted to Dr. Theodore C. Jane way.

Haven Emerson.

New York, 1912.

INTRODUCTORY

It was with much satisfaction that I gave my hearty approval to the republication, with additions, of Flint's Manual of Auscultation and Percussion. This I regard as a fitting tribute to the memory of its distinguished author, as it extends to present and future students of medicine the benefits of the teachings he so loved to impart.

The letter-press has been retained with but slight alteration, for the book was a masterpiece of clarity and precision. Few medical writers have been gifted with the elegance of diction illustrated in this little work.

The additions by the editor to the original chapters embrace certain new and valuable methods of examination that have arisen within the last twenty-five years.

In the interest of completeness new chapters have been added, giving methods of physical examination of the abdominal viscera, and of the nervous system.

Austin Flint.

New York, 1912.

Chapter I Introduction

Definition of percussion and auscultation — The sounds obtained by these methods of representing healthy and morbid physical conditions— Definition of signs — The basis of our knowledge of signs the constancy of association of certain sounds with certain physical conditions in health and disease — The present state of perfection of our knowledge of signs furnished by auscultation and percussion — Requirements for the successful study of these methods of exploration — The anatomy and physiology of the chest — An enumeration of the points relating thereto which are of special importance — The physical condition incident to the different diseases of the chest: the conditions relating to the respiratory system stated, and a summary of them — The distinctive characters of healthy and morbid signs; variations in intensity, pitch, and quality, considered as the chief source of the character distinguishing the signs of disease from each other and from those of health — Other distinctions than those of intensity, pitch, and quality — The analytical method of the study of auscultation and percussion — The signifiance of signs as regards the physical conditions which they severally represent — Morbid conditions, not individual diseases represented by the morbid signs — Regional divisions of the chest — Anatomical relations of the regions severally to the parts within the chest.

PHYSICAL EXPLORATION

The physical examination of the chest embraces six different methods — namely, inspection, palpation, mensuration, percussion, auscultation, and succussion. Of these, percussion, auscultation, and succussion dealing with sounds involve the sense of hearing. In percussion the sounds are produced by striking upon the walls of the chest; in auscultation, they are caused by acts of breathing, speaking, and coughing, in succussion they are caused by splashing of fluids when the body is shoved abruptly, or shaken.

The sounds in auscultation and percussion are (1) normal or healthy sounds, being produced when there is no disease of the chest; and (2) abnormal or morbid sounds, being produced when the chest is the seat of disease. The sounds, healthy and morbid, constitute what are known as physical signs. Frequently, for the sake of brevity, the term signs, without the word physical, is used to denote these sounds. Conventionally, physical signs, or signs, are terms employed in a sense of contradistinction to the term symptoms. The signs are distinguished, of course, as normal or healthy, and abnormal or morbid.

The sounds which constitute signs represent certain physical conditions pertaining to the chest. The normal or healthy signs represent physical conditions existing when the organs are not affected by disease; the abnormal or morbid signs represent physical conditions which are deviations from those of health, being incident to the various diseases of the chest. The physical conditions represented by signs may be distinguished as normal or healthy, and abnormal or morbid conditions.

The representation of healthy and morbid physical

PHYSICAL EXPLORATION 19

conditions by certain healthy and morbid signs is established by having ascertained a constancy of association of the signs with the conditions. This constancy of association is ascertained by observation or experience. The sounds obtained by percussion and auscultation in health are thereby established signs of healthy conditions, and the sounds obtained only in cases of disease are thereby established signs of morbid conditions. Our knowledge of certain sounds as the signs of certain physical conditions can have no reliable basis other than the constancy of the connection of the former with the latter. This constancy of connection is determined by the study of the sounds during life and examination of the organs after death. The existence of certain conditions is not to be inferred from the characters of certain sounds until the connection of the sounds with the conditions has been ascertained by experience; then, and then only, are the sounds to be reckoned as signs of these conditions. So, also, it is not to be inferred from certain physical conditions found after death, that certain sounds must have been produced during life, until the connection between the conditions and the sounds has been ascertained by experience. In other words, our knowledge of signs as representing physical conditions, can rest on no other than a purely empirical foundation.

Our knowledge of the signs representing the physical conditions in health and disease, thanks to the labors of Laennec, and of those who have followed in his footsteps, has been brought to great perfection. 1 The practical object of this knowledge is to determine by means of auscultation and percussion, together with the other methods of exploration, the existence of either healthy or morbid physical conditions, and to discriminate the latter from each other; that is to say, the practical object is diagnosis. The signs now known to represent physical conditions, healthy and morbid, taken in connection with symptoms and pathological laws, render, for the most part, the diagnosis of diseases of the chest easy and positive. Hence, it becomes the duty of the medical student and practitioner to give to auscultation and percussion attention sufficient, at least, for their practical application to the diagnosis of the diseases commonly met with in medical practice; and this duty is the more imperative because it involves neither peculiar difficulties nor great labor. In entering upon the undertaking it is important to consider the requirements for the successful study of this province of practical medicine. These requirements relate to: (1) the anatomy and physiology of the chest; (2) the morbid physical conditions incident to the different diseases of the chest; (3) the distinctive character of healthy and morbid signs; and (4) the signifiance of the signs as regards the physical conditions which they severally represent.

1 We owe a debt also to Auenbrugger, who preceded Laennec, and to Wintrich, Skoda, Traube, and Gerhardt particularly among his successors.

ANATOMY OF THE RESPIRATORY ORGANS 21

ANATOMY AND PHYSIOLOGY OF THE RESPIRA- TORY ORGANS

The necessity of a knowledge of the antomy and physiology of the chest, as a requirement for the study of auscultation and percussion, together with the other methods of physical exploration, is too obvious to need any discussion. The physical conditions of health must be known as preparatory for appreciating the physical conditions of disease. It would be absurd to think of studying the latter until the former are known. The student, therefore, who is not acquainted with the anatomy and physiology of the chest, must defer entering upon the study of physical diagnosis until this requirement is fulfilled. Familiarity with the morbid physical conditions is necessary; and for the advanced medical student or the practitioner it is advisable to refresh the memory with a reviewal of certain anatomical and physiological points before beginning the study of auscultation and percussion. These points, relating especially to the physical conditions of health, cannot be considered in this work. A simple enumeration of them only can be introduced, the reader being referred for details to treatises on anatomy and physiology.

Important anatomical conditions relate to the bones of the chest — namely, the general conformation of the thorax, the differences in respect of the obliquity of the ribs from above downward; the direction of the costal cartilages, their connection with the sternum, and the angles formed by the junction of the ribs and cartilages; the differences in width of the intercostal spaces in the upper, middle, and lower portions of the anterior, lateral, and posterior aspects of the thorax, together with the relations of the scapula and clavicle. The relative thickness of the muscular covering of the chest in different situations is to be considered, and, in women, the varying size of the mammae. The attachments of the diaphragm to the thoracic walls, and its relations to the organs below, as well as above it, are points of importance (Figs. 1, 2, 3, 4).

Important physiological conditions relate to the parts which the ribs, costal cartilages, sternum, and diaphragm severally play in the movements of respiration. The differences, in respect of these movements, in tranquil and in forced breathing, the contrast between the two sexes, and between early and advanced life, are points to be studied. Other points are, the frequency of the respirations in health, and the relative duration, rapidity, and force of the inspiratory and the expiratory movements.

Certain anatomical and physiological points pertain to the organs within the chest. The more important of these, relating to normal physical conditions, are the following: (1) As regards the lungs, the connections of the pleura, and the smoothness of the pleural surfaces in contact with each other; the relations of the apex and base of each lung to the chest-walls, and the differences of the two lungs in this respect; the relative spaces occupied respectively by the two lobes of the left, and the three lobes of the right lung;

PHYSIOLOGY OF THE RESPIRATORY ORGANS 23

the situation of the interlobar fissures in either side on the posterior, lateral, and anterior aspects of the chest; the arrangement of the air- vesicles, pulmonary lobules, and the different-sized intra-pulmonary bronchial tubes; the expansion of the air- vesicles, and the movement of the current of air from larger to smaller bronchial tubes in the act of inspiration, the vesicles diminishing in size, and the current of air moving from smaller to larger tubes in the act of expiration; the difference in respect to the relative proportion of air and solids at the end of inspiration and at the end of expiration; the extent to which the volume of the lungs may be diminished by a forced act of expiration, and increased by a forced act of inspiration; the relations of the apices to the subclavian arteries, and the variable extent to which the apex rises on either side above the clavicle. (2) As regards the larynx, trachea, and the bronchial tubes without the lungs; the anatomy and physiology of the vocal chords ; of the muscles concerned in the movements of respiration and of phonation, with the relations of each to the recurrent laryngeal nerve; the size of the rima glottidis in youth, after puberty, and relatively in the two sexes; the enlargement of the rima in the act of inspiration, the diminution of its size in the act of expiration, and the closer approximation of the chords in the act of coughing; the difference in the amount of areolar tissue above the vocal chords in children and in adults; the situation of the trachea and the point of its bifurcation; the length, direction, and size of the two primary bronchi contrasted with each other, and the branches which penetrate the lungs. (3) As regards the heart, the boundaries of the space which it occupies — that is, of the precordial space; the relation of the aorta and pulmonic artery to the walls of the chest; the portions of the precordial space in which the heart is covered and uncovered by lung; the situations of the auricles and ventricles respectively; the relations of these to each other, and the arrangements of the valves; the currents of blood through the orifices within the heart, and the relations of each of these to the heart-sounds; the rhythmical succession of these sounds; the differences which distinguish each from the other in respect of loudness, duration, tone, quality, extent of diffusion, and the situation in which each has its maximun of intensity; the mechanism of these sounds, and the situation of the apex-beat (Figs. 1, 2, 3, 4).

The foregoing are the anatomical and physiological points which especially claim attention with reference to normal physical conditions, preparatory to entering on the study of abnormal physical conditions represented by the signs furnished by auscultation and percussion together with the other methods of physical exploration.

It is recommended to the student, before proceeding farther, either to acquire or review knowledge respecting all these points. Knowledge of these should be made familiar, if it be not already so, by reference to works treating of the anatomy and physiology of the chest.

DISEASES OF THE RESPIRATORY SYSTEM 25

THE MORBID PHYSICAL CONDITIONS INCIDENT

TO THE DIFFERENT DISEASES OF THE

RESPIRATORY SYSTEM

The various morbid physical conditions incident to different diseases must be known, for it is the immediate object of auscultation, percussion, and the other methods of exploration, to ascertain either the existence or the absence of these morbid conditions. Knowledge of all the important conditions which are deviations from those of health, and the relations of each to different diseases, is, therefore, an essential requirement.

Deviations from the normal conformation of the chest and the various abnormal movements of respiration, belong properly among the physical signs obtained by inspection, palpation, and mensuration. For the most part, these signs represent morbid physical conditions within the chest. Certain conditions relate to the presence of liquid, either serous, sero-fibrinous, or purulent, within the pleural sac. The quantity of liquid may be large enough to compress the lung into a solid mass, and to enlarge the affected side, at the same time restraining or annulling the respiratory movements; the chest on the affected side, then, will contain only lung solidified by compression, and liquid. In other cases the quantity of liquid is either small, moderate, or considerable, the lung then containing a lessened quantity of air, and its volume diminished in proportion to the amount of liquid. These morbid conditions are incident to simple pleurisy with effusion, pyothorax or empyema, and hydrothorax.

The pleural surfaces, in cases of pleurisy, may be more or less covered with recent fibrinous exudation, and, when not separated by the presence of liquid, they do not move upon each other smoothly and noiselessly. The friction of the opposed surfaces is still more productive of audible and sometimes tactile signs after the absorption of liquid, when the exudation has become more adherent and dense than when it is recent.

The presence of air in the pleural space, either alone or with more or less liquid, in pneumothorax, may compress the lung into a solid mass, also dilating the affected side, and restraining or annulling its movements; and the air, with or without liquid, when not in sufficient quantity to produce these effects, may diminish more or less the volume of the lung and the amount of air in the pulmonary vesicles. These morbid conditions give rise to characteristic physical signs. The perforation of lung, usually existing in cases of pneumothorax, occasions additional signs which are characteristic.

Solidification of lung is an important physical condition incident to several diseases, irrespective of the condensation, just referred to, caused by the compression of liquid or air in the pleural sac. Complete consolidation of an entire lobe, or of two and even three lobes, exists in the second stage of lobar pneumonia. Certain physical signs represent this

DISEASES OF THE RESPIRATORY SYSTEM 27

condition of complete solidification. 1 The different degrees of solidification, namely, slight, moderate, and considerable, occur during the stage of resolution in cases of pneumonia, and these gradations are severally represented by well-defined characters pertaining to physical signs. Solidification, circumscribed, forming nodules which vary in size and number, situated in the upper, lower, or middle portion of the lung, either on one side or on both sides, exists in phthisis, in broncho-pneumonia and collapse of pulmonary lobules, in hydatids, in hemorrhagic infarctus and embolic pneumonia, in pulmonary gangrene, and in primary and secondary neoplastic growths. It exists, greater or less in degree and more or less extended, in interstitial pneumonia. In these different connections the existence of solidification, its degree and extent, its limitation to one situation or its existence at different points, are determinable by means of physical signs.

A morbid condition the opposite of solidification is an abnormal accumulation of air within the air-vesicles of the lungs. This is incident to pulmonary or vesicular emphysema, involving a morbid dilatation of the air-vesicles. The permanent expansion and increased volume of the upper lobes in some

1 The term complete consolidation as used here is not intended to indicate a filling of the large subdivisions of the bronchi with exudate in the affected lobe. This extreme condition may occur and is described as massive consolidation. In this form certain of the physical signs are markedly altered, the breath and voice sounds being diminished or entirely suppressed.

cases of this disease, occasion a characteristic deformity of the chest, together with certain deviations from the normal movements of respiration, which are also characteristic. This morbid condition is represented by distinctive signs furnished by auscultation and percussion. The extravasation of air in the connective tissue, constituting interlobular and subpleural emphysema, in like manner gives rise to signs furnished by these methods of exploration.

The presence of a viscid exudation within the air-vesicles and bronchioles, is a morbid physical condition incident to acute pneumonia, especially in its first stage, agglutinating the cells and bronchioles, the walls of which may be brought into contact or close proximity at the end of the act of expiration. The separation of the walls thus agglutinated, in the act of inspiration, gives rise to an auscultatory sign (the crepitant rale).

An accumulation of serum within the air-vesicles constitutes the condition called pulmonary edema. This condition gives rise to signs furnished by auscultation and percussion.

Liquid within the bronchial tubes (serum, pus, blood, or thin mucus) is a condition incident to pulmonary edema, abscess either of the lung or situated elsewhere and evacuating through the bronchial tubes, phthisis, bronchorrhagia, pneumorrhagia, bronchorrhea, and bronchitis. The passage of air through the different varieties of liquid in the tubes causes bubbling sounds which are appreciable in auscultation. The apparent size of the bubbles (coarseness or

DISEASES OF THE RESPIRATORY SYSTEM 29

fineness) denotes the size of the tubes in which they are produced, and the pitch of the bubbling sounds denotes either solidification or otherwise of the pulmonary substance surrounding the tubes in which the bubbles are produced. Bubbling sounds more intense and on a larger scale are caused by the presence of liquid within the trachea and larynx, known as the tracheal rales or the death rattle.

Diminished calibre of the bronchial tubes within the lungs, either localized or diffused, is a condition due to the presence of tenacious mucus, and the swelling of the mucous membrane in cases of bronchitis. In cases of so-called capillary bronchitis the condition may involve an alarming degree of obstruction. The same morbid condition is incident to bronchial spasm in asthma, occasioning in this disease great suffering, but without immediate danger. The condition is represented by auscultatory signs which enable the auscultator to differentiate the obstruction due to capillary bronchitis from that due to bronchial spasm. Permanent obliteration of more or less of the bronchial tubes is an occasional morbid condition.

Obstruction of a bronchial tube, either within or without the lung, is a morbid condition involving the loss of respiratory sound within the area of the bronchial branches and vesicles not receiving air in consequence of the obstruction. The obstruction may be temporary, being caused by a plug of mucus of sufficient size to prevent the passage of air; the morbid condition is then incident to bronchitis. One of the primary bronchi may be obstructed temporarily by a plug of mucus, and obstruction of the larynx in childhood thus produced may be sufficient to cause death by suffocation. The inhalation of foreign bodies is another cause of obstruction within the larynx, trachea, or bronchi. A primary bronchus or the trachea may be pressed upon by an aneurismal or other tumor, and, in this way, more or less obstruction to the passage of air is produced. However produced, the situation of the obstruction and its degree are, in general, determinable by means of auscultatory signs.

Dilatation of bronchial tubes occasions two morbid physical conditions differing as regards their auscultatory signs — namely, (1) an enlargement of greater or less extent, the tubes preserving their cylindrical form; and (2) a sacculated enlargement. The former occurs generally in connection with solidification around the tubes from hyperplasia of the areolar tissue, and is thus incident to interstitial pneumonia. The latter may give rise to signs which represent pulmonary cavities.

Sacculated dilatations of bronchial tubes, and the cavities incident to phthisis, pulmonary abscess and circumscribed gangrene of lung, are represented by well-marked and highly distinctive signs furnished by auscultation and percussion. The signs denote either that cavities have flaccid walls which collapse in expiration and expand in inspiration, or that, owing to solidification of lung, they remain open during both acts of respiration.

More or less of the space within the chest which, normally, is occupied by lung, may be encroached upon by aneurisms or other intra-thoracic tumors. This is a physical condition giving rise to notable morbid signs furnished by auscultation and percussion.

Finally, an extremely rare morbid physical condition is the presence of more or less of the hollow viscera of the abdomen within the chest, in consequence of either a congenital deficiency in the diaphragm, or a wound penetrating this muscle (diaphragmatic hernia).

The foregoing morbid physical conditions relate to the respiratory organs. Those relating to the heart are deferred in order that they may precede more immediately an account of the signs of cardiac disease. As a requirement for the study of morbid physical signs, the foregoing morbid physical conditions must be understood and memorized. To assist the student in the latter, a summary of these conditions is appended.

SUMMARY OF MORBID PHYSICAL CONDITIONS

INCIDENT TO DISEASES OF THE

RESPIRATORY ORGANS

1. An accumulation of serous, sero-fibrinous, or purulent liquid sufficient to fill the affected side of the chest, and sometimes causing more or less enlargement.

2. An accumulation of liquid partially filling the affected side of the chest, the quantity being either small, moderate, or considerable.

3. Fibrinous exudation on the pleural surface.

4. Air with liquid within the pleural cavity, and perforation of lung.

5. Air without liquid in the pleural cavity.

6. Solidification of lung, either complete or approximating to completeness.

7. Solidification of lung, slight or moderate in degree.

8. Dilatation of the air-vesicles, involving within them an abnormal accumulation of air.

9. Extravasation of air within the pulmonary connective structure.

10. Exudation within air- vesicles and bronchioles.

11. Liquid within air- vesicles.

12. Liquid (mucus, serum, pus, or blood) within bronchial tubes of large, medium, or small size.

13. Liquid within bronchial tubes of minute size.

14. Obstruction of the pulmonary bronchial tubes by mucus, swelling of the mucous membrane, and spasm of the bronchial muscular fibres.

15. Obstruction of larynx, trachea, or bronchi exterior to the lungs, by plugs of mucus or foreign bodies.

16. Obstruction of the trachea or a primary bronchus by aneurismal or other tumors.

17. Dilatation of bronchial tubes, cylindrical or sacculated.

18. Pulmonary cavities.

19. Tumor within the chest.

20. Diaphragmatic hernia.

CHARACTERS OF HEALTHY AND MORBID SIGNS 33

THE DISTINCTIVE CHARACTERS OF HEALTHY AND MORBID SIGNS

For the practice of auscultation and percussion it is essential to be able to recognize the signs, severally, which represent the different physical conditions in health and disease. It is essential to distinguish the morbid from the healthy signs, and to discriminate from each other, severally, the signs of disease. The recognition and discrimination of signs require knowledge of the distinctive characters belonging to each of them. In entering upon the study of the signs, therefore, it is a necessary requirement to know whence their distinctive characters are derived. To this point of inquiry the attention of the student is now invited.

The signs being sounds, they are to be recognized and discriminated in the way in which we practically recognize and discriminate other sounds. It is not necessary, in order to do this, to study the science of acoustics. In becoming familiar with other sounds, for example, musical notes produced by different instruments, or the varieties of the human voice, we do not have recourse to that science. It suffices for all practical purposes to contrast the sounds obtained by auscultation and percussion with reference to very simple and obvious differences; and, yet, it is necessary to understand very clearly in what these differences consist, or, in other words, the sources of the distinctive characters of these sounds. The 3 more important of the differences between the sounds obtained by auscultation and percussion relate to intensity, pitch, and quality. The distinctive characters of most of the signs are derived from these three sources. In becoming practically acquainted with the signs, they are to be contrasted as regards intensity, pitch, and quality, precisely as we would bring other sounds into contrast in these three aspects. The distinctive characters of the signs, severally, are especially derived from their differences in these respects. The distinctions expressed by the terms intensity, pitch, and quality are, therefore, to be made clear.

Differences in the intensity of sounds are easily understood. One sound is more intense than another sound when it is simply louder, and varying degrees of intensity are expressed by such terms as feeble or weak and loud, to which may be prefixed adjectives of quantity, such as very, moderate, etc. This is all that need be said with reference to the first of the three aspects under which sounds are contrasted. It will be seen hereafter that intensity is an essential element in the distinctive characters of certain of the signs.

Differences in the pitch of sounds are easily understood by those who have given any attention to music. The differences are expressed by the terms high and low, to which may be prefixed words denoting a greater or less degree of highness or lowness. A nice appreciation of variations in the pitch of musical notes, requires what is known as a " musical ear;" but a

CHARACTERS OF HEALTHY AND MORBID SIGNS 35

very nice appreciation is not essential in comparing, as regards pitch, the sounds studied in auscultation and percussion. For the most part, these sounds are not musical notes; nevertheless, differences in pitch are readily perceived. A musical ear is undoubtedly an advantage in readily distinguishing differences in pitch; but it is by no means a sine qua non. For those who have given no attention to music, some difficulty may be at first experienced in judging correctly of differences in this regard; but the difficulty disappears after a little practice. Differences in pitch now enter pretty largely into the distinctive characters of physical signs; but by Laennec, and those who immediately followed him, comparatively little attention was paid to the study of signs with reference to these differences. The writer was led to engage in this study more than a quarter of a century ago, and hereafter, in giving an account of the different signs, he will claim to have been the first to have clearly indicated certain characters from this source. 1 Differences relating to quality are apt, at first, to be confounded with those relating to pitch; hence the distinction between pitch and quality must be clearly understood. We may say of the quality of a sound, that it embraces whatever is not embraced in the terms intensity and pitch. This is true as a general statement. The sense of the term quality, in distinction from intensity and pitch, may be most

1 Vide Prize Essay on "Variations of Pitch in Percussion and Respiratory Sounds, and their Application to Physical Diagnosis." Transactions of the American Medical Association, 1852.

readily made clear by an illustration. Let it be supposed that we bear the notes of an instrument which is unseen — the performer, for example, being in another room. We recognize at once the instrument by the notes, provided it be one with which we are familiar, such as a violin, a flute, a clarionet, etc. We do not need to see the instrument; we recognize it by the sounds. Now, how do we recognize it? Certainly not by the intensity of the sounds; it matters not whether these be loud or weak, so that we hear them. Certainly not by the pitch; for if a piece of music be performed, we get both high and low notes. We recognize the instrument by the quality of the sounds. Each musical instrument, owing to its peculiarity of construction, yields sounds which are peculiar to it; and after we have become familiar with the quality of sounds peculiar to an instrument, we immediately thereby recognize it. Precisely in the same way we may recognize certain sounds produced by auscultation and percussion in health and disease. The signs differ in quality according to the physical conditions which they severally represent; and differences in quality will be found hereafter to constitute essential and obvious distinctions by which the signs of health and disease are recognized and discriminated. This is a source ot some of the most distinctive of the characters of certain of the physical signs.