753 



AURIC ACID. 1 



AUSCULTATION. 



764 



Gewichte, Miinrfiisze, und Masse des Alterthums in ihrem rusammen- 

 hange,' Berlin, 1838 ; Hussey, ' Ancient Weights and Money,' and H. 

 Noel Humphrey, ' Coin Collector's Guide.' 



AURIC ACID. [GOLD.] 



AURI'GA, the Charioteer, a constellation situated between Perseus 

 and Gemini. It is represented as a man holding a bridle in the right 

 hand and supporting a goat and kids on the left arm. The star in the 

 body of the goat, called Capelia (and Alioth by the Arabs) is of the 

 first magnitude, and presents the best guide to the constellation. 

 There is no satisfactory account of the mythology of this figure. It is 

 said to have been the Horus of the Egyptians ; among the Greeks, the 

 human figure is by different writers called Erichthonius, Bellerophon, 

 Hippolytus, &c. ; while the goat is Amalthsea, the foster-mother of 

 Jupiter. But this explanation is even more unsatisfactory than most 

 others, owing to the want of apparent connection between the figures 

 of the group. 



The following are the principal stars in this constellation : 



No. in Catalogue 

 No. in Catalogue of British 

 Character. of I lamstccd. Association. 



c 



a 

 5 



I 



3 



7 



8 



13 



33 



34 



37 



44 



1520 

 1540 

 1541 

 1613 

 1885 

 1895 

 1900 

 2001 



Magnitude. 



4 



4 



4 



1 



35 



2 



4 



4 



AURIPIGMKNTUM. [ARSENIC, TERSULPHFDE OF.] 



AUROCYANIDES. [GOLD.] 



AUROHYDROCYANIC ACID. [GOLD.] 



AURORA. [Eos.] 



AURORA BOREALIS. [POLAR LIGHTS.] 



AUSCULTATION, from ausculto to listen, the method of distin- 

 guishing the states of health and disease by the study of the sounds 

 produced by the organs in the movements which they make in the per- 

 formance of their functions. When air rushes by the wind-pipe into 

 the lung in the action of inspiration ; when it is expelled through the 

 same tube in the action of expiration ; when it is acted upon in the larynx 

 by the organs of the voice ; when the heart beats, that is, when the 

 different chambers of which it is composed forcibly contract ; when 

 the blood flows through the great arterial trunks ; when air is con- 

 tained in the intestines and is acted on by these organs in their natural 

 movement*, in all these cases sounds are produced which can be 

 heard, often by the unassisted ear; and still more distinctly by the aid 

 of an acoustic instrument. When attention is paid to these sounds, it 

 is found that they differ greatly from each other. The sound of the 

 air in the wind-pipe during inspiration is different from that in the 

 same tube in expiration ; the sound of the air in the larynx during the 

 act of speaking is different from both ; while the sound produced by 

 the action of the heart, and even by the action of its different chambers, 

 may be discriminated the one from the other. By the study of these 

 sounds, it is obvious that it may be possible to become acquainted 

 with those which are natural to the different organs in the state of 

 health : but when these organs become disordered, their movements 

 are modified in a great variety of modes, each modification of move- 

 ment being attended with a corresponding modification of sound ; con- 

 sequently, these modified sounds are capable of affording indications of 

 various states of disease, the difference between the healthy and the 

 morbid sound being the sign and the measure of the deviation of the 

 organ from the state of health. The physician, carefully studying the 

 sounds produced by the organs during life, makes himself familiar with 

 those which are natural to them : in a particular case he hears sounds 

 which he knows to be altogether different from those that are natural : 

 the patient dies ; the physician examines the organs after death ; he 

 finds that a certain organ is diseased in a certain mode ; this morbid 

 condition of the organ, which he has been taught by inspection after 

 death, he associates in his mind with the peculiar sound which be 

 observed that the organ emitted during life. Another case, attended 

 with the same sound, is proved by inspection after death to be con- 

 nected with the same disease of the same organ : and every time that 

 he hears this peculiar sound, he finds the same organ diseased in the 

 same mode. A peculiar sound may thus become the sure and certain 

 indication of a particular disease ; in this manner, by persevering 

 attention during life and careful examination after death, it may be 

 possible to discriminate the morbid states of all the organs that give, 

 when in action, a distinguishable sound. Extended and repeated 

 observation has shown that the detection and discrimination of disease 

 by this mode may be effected with a minuteness and precision that 

 coulB not possibly have been credited previous to the practical demon- 

 stration of the fact; and modern science has elicited, and almost 

 matured, a new mode, an intention novum,ae one of the first suggestors 

 of the method justly termed it, of discovering the morbid states of 

 several of the most important organs of the body. 



To the philosophical mind nothing is more interesting and instructive 

 than to trace th history of uaef ul discovery. It is clear that the idea 



ABTS AND 8CI. DIV. VOL. X. 



on which the modern art of auscultation is founded, had occurred to 

 Hippocrates upwards of two thousand years ago. " You will know by 

 this," says this first recorded observer of disease as denoted by sound, 

 " that the chest contains water and not pus, if, on applying the ear for 

 a certain time to the side, you hear a sound like that of boiling 

 vinegar." The non-existence of dissection in the age and country of 

 Hippocrates prevented all accurate and extended observation ; and con- 

 sequently rendered it impossible to follow out to any sure and useful 

 result the idea which had occurred to the most ancient writer on 

 physic. Accordingly, the suggestion of Hippocrates seems to have 

 attracted no attention for many centuries, and the mode of studying 

 disease founded upon it, if it had ever been carried to any extent in 

 remote ages, had long sunk into oblivion. 



About the middle of the 17th century, a distinguished philosopher 

 and mathematician, who was not of the medical profession, and who 

 does not appear to have been acquainted with the writings of Hippo- 

 crates, had the penetration to see that advantage might be taken of the 

 sounds produced by the motions of the internal organs to discover the 

 nature of their diseased states, and he even predicted that artificial 

 means would some day be employed to assist the ear in the pursuit of 

 that object. " There may be a possibility," says Hooke, in his posthu- 

 mous works, " of discovering the internal motions and actions of bodies 

 by the sound they make. Who knows but that, as in a watch, we may 

 hear the beating of the balance, and the running of the wheels, and the 

 striking of the hammers, and the grating of the teeth, and multitudes 

 of other noises ; who knows, I say, but that it may be possible to 

 discover the motions of internal parts of bodies, whether animal, vege- 

 table, or mineral, by the sounds they make : that one may discover 

 the works performed in the several offices and shops of a man's body, 

 and thereby discover what engine is out of order, what works are 

 going on at several times, and lie still at others, and the like. I have 

 this encouragement not to think all these things utterly impossible, 

 though never so much derided by the generality of men, and never so 

 seemingly mad, foolish, and fantastic; that, as the thinking them 

 impossible cannot much improve my knowledge, so the believing them 

 possible may perhaps be an occasion for taking notice of such things as 

 another would pass by without regard as xiseless. And somewhat more 

 of encouragement I have also from experience, that I have been able 

 to hear very plainly the beating of a man's heart ; and it is common to 

 hear the motion of the wind to and fro in the guts and other small 

 vessels : the stopping in the lungs is easily discovered by the wheezing. 

 As to the motion of the parts one amongst another, to their becoming 

 sensible, they require either that their motions be increased, or that 

 the organ be made more nice and powerful to sensate and distinguish 

 them as they are ; for the doing of both which I think it is not im- 

 possible but that in many cases there may be helps found." 



This prediction has been realised : helps have been found. About a 

 century after this passage was written, Leopold Avenbrugger, a German 

 physician then residing at Vienna, fell upon an artificial method of 

 producing sounds in various regions of the body [PERCUSSION ; AVEN- 

 BRUOGER, Bioo. DIV.] by which the physician might judge of the 

 state of the subjacent parts. This method, announced to the world 

 in a small volume in Latin, first published in the year 1761, attracted 

 little attention either among the countrymen of the inventor or 

 among foreign nations for the space of half a century. It was trans- 

 lated into French by Roziere in 1770. In the year 1808, the celebrated 

 Corvisart again translated it, and made his method known to all 

 the countries of Europe. From that period the practice of percussion 

 has been pretty general, and it soon became attended, in skilful hands, 

 with results far more precise and certain than had been anticipated. 



The attention of physicians having been thus distinctly directed to 

 the method of studying disease from sounds produced in the body 

 whether naturally or artificially, a number of young French physicians, 

 disciples of Corvisart, about the commencement of the present century, 

 took up the subject with extraordinary zeal. Among the most dis- 

 tinguished of these young men were MM. Double, Bayle, and Laennec. 

 Speaking of the signs furnished by respiration, and of the sounds 

 produced by it within the chest, M. Double, in his work on Semeiology, 

 published two years before the discovery which led to the establish- 

 ment of auscultation as an art and science, says, " In order to hear 

 distinctly the sounds within the chest, we must apply the ear closely 

 to every point of all its aspects, by which means we can distinguish 

 not merely the kind and degree of the sound, but even its precise site. 

 I have frequently derived great benefit from this mode of investigation, 

 to which I was naturally led by the employment of the like method in 

 exploring the pulsation of the heart." 



At the very time when this was written, Laennec and several of his 

 fellow-pupils, under the guidance of their master, Corvisart, while 

 diligently studying chest diseases by means of percussion, met occa- 

 sionally with cases in which this method afforded them little or no 

 assistance ; and in the hope of obtaining further aid, they accustomed 

 themselves in such cases to apply the ear closely to the chest. Little 

 practical benefit resulted for some time : but at length it led to a dis- 

 covery of inestimable advantage ; a discovery which may be said to 

 have enabled the physician to see into the chest almost with as much 

 clearness as if its walls were transparent. The following is the account 

 of this discovery in the words of the remarkable man who made it, and 

 who in the course of a few years, with a diligence scarcely ever 



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