auscultator, the presence of two very different conditions of lung on the two sides of the chest when the disease is confined to one part, as is usual at the first period of the malady. The bronchnoea sounds in the first stage being usually feeble, short, and defective, they make very little impression on the ear, when this is conveyed to one ear only, and this deficiency is contrasted with the full vesicular, rustling, noisy respiration sound of healthy lung conveyed to the other ear, or it may be the same ear, by an immediately succeeding observation. To be perhaps more explicit, it may be said that the successive auscultation of the healthy and the unhealthy lung by means of this instrument, which virtually takes observations from two parts and with great ease for the two ears respectively, affords great advantages for the mind discovering the difference between the character and extent of the respiratory sounds of the two parts. And it is to be observed, that a more satisfactory perception of the differences which exist is thus obtained than by the successive application of the wooden stethoscope, as has been already observed, and as will be further dwelt upon when the properties of this instrument offer themselves for special notice at a subsequent part of this work.

The bronchnoea bruits of the first stage of phthisis, located on one side, are usually feeble and defective as compared with the respiration sound of healthy lung upon the opposite side, more particularly so when, as generally happens, the respiration on this side has become puerile or compensatory. If the bronchnoca bruits are characterised more by the absence of the fine friction sounds of vesicular respiration, and less by the adventitious character of blowing or loud whiffing, the respiration sound is then remarkable more for negative than for positive characters. It is rather the ordinary respiration sound deprived of much of its fine friction or rustling character, and is therefore very much a form of ordinary respiration sound, minus a certain quality. This naturally prepares us for the following important diagnostic fact, valuable at once in auscultation, and curious as an auditory phenomenon.

When the two ears are separately connected by means of the differential stethoscope, with a tuberculated bronchial breathing lung, such as is described above, and with a healthy lung at the same moment, the vesicular full respiration of the healthy side is recognised through the ear connected with it, and the bronchial defective ill-formed respiration sound of the unhealthy lung is not at all perceived through the ear connected with it. The ear connected with the bronchnoa lung is deaf, as it were, while the other ear connected with

the vesicular breathing lung is rendered particularly alive to the sounds conveyed to it. It is a curious fact, and one which shall be explained hereafter, that while the ear employed by means of the stethoscope upon the bronchnoa lung, carries no impression whatever of the peculiar breathing of the part, its employment in this way increases the sensation of vesicular respiration exclusively heard, as it were, through the other ear. The vesicular full respiration sounds conveyed to one ear eclipse simple, quiet bronchial respiration sounds conveyed simultaneously to the other ear in the same manner, and as effectually as full vesicular respiration sound eclipses defective vesicular respiration sound, as has been already described. To ascertain whether the respiration sounds which are eclipsed be defective vesicular respiration sounds, or quiet non-blowing or whiffing bronchial bruits, is a matter of the greatest ease. We have simply to take an observation of the unhealthy part with one ear, and with one limb of the stethoscope. The vesicular or the bronchial character is then satisfactorily ascertained by this single and separate act of uno-aural audition. When, however, the bronchial respiration assumes a blowing, loud, whiffing character, which it occasionally does, much more frequently it is true, in the third stage of phthisis than in the first, it effectually eclipses the vesicular respiration of the sound lung if this be not particularly loud. The loud sound of blowing tubular respiration heard through one ear, and the absence of sound in the other ear, convince the mind at once that a very serious difference in the conditions of the two lungs exists. The auscultator being thus unmistakably assured of this, proceeds narrowly to detect the precise character of the two sounds respectively, and satisfactorily determines the precise physical conditions of the parts, and he does this by now examining them separately or in succession.

It occasionally happens that the inspiration of bronchnoa respiration is loud and blowing, while the expiration sound is feeble and indeterminate. In this case, when the differential stethoscope is simultaneously employed for the two ears on healthy and unhealthy lung respectively, the bronchial breathing only is heard in one ear and the vesicular respiration is heard in the other. Now we have bronchial inspiration sound on one side, oscillating, as it were, or alternating, with vesicular expiration sound on the other. This alternation of sound obtains occasionally, in the first stage of phthisis, but it is much more rare than oscillation, so to speak, of bronchial

expiration sound on one side, with vesicular inspiration sound on the other. This is, however, more frequently found in phthisis in its third stage, marked by dry cavities, having bronchial outlets offering resistance, and with puerile breathing lung on the opposite side. When this form of oscillation of sound from one side to another is perceived, the first stage of phthisis has generally been long passed, the third has often arrived, and therefore this point may more properly be dwelt upon at a later period than at the present

moment.

The mechanism of bronchial respiration sounds must be obvious from the description which has just been given of them. However, it may be well to say, that the sounds are produced by the motion of air passing in and out of tubes; bronchial tubes, varying in size from a quill to the little finger. Friction is produced, and the tubes and the passing air are thrown into sonorous undulations. The pressure exerted upon the tubes by the surrounding solid tubercle and condensed pulmonary structure aids in the production of friction. The rapidity and force of the respiratory acts, now considerably augmented, further tend to the induction of friction, and therefore of sound. When air passes along a tube of the calibre referred to, with freedom and ease, the tubular sound will be recognised, but it will be destitute of the blowing character which we have said bronchnœa sometimes possesses. It is when the tubes are constricted or pressed upon to some considerable extent, and when the air is passed along with force, that we have constriction and harsh blowing sounds. When tubes which are situated as we have above described become free from constriction and pressure, as may be the case on the formation of cavities, this constrictive character of sound ceases. When tubes which have been emitting sounds become altogether occluded by increasing pressure, or by the formation of plugs of lymph, and mucus, and blood, tubular sounds cease altogether. If the force of air passing along be very slight, the friction may be too feeble to produce sufficiently rapid vibrations in the solids for the induction of sound. A firm tube surrounded by firm heavy structure will be indisposed to vibrate with a slight force. But on the other hand, firm structure will serve well to communicate the actually produced sound to the thoracic walls. Condensed lung structure has long been believed to conduct in a superior manner, bronchial sounds to the walls of the thorax, yet there is no doubt whatever that if weight and firmness be very great in proportion to the

sound-producing movements, then they will prove unfavourable to sound, not only by a deficiency of conducting power, but by operating against the production or origination of sound. I have found by experiment that vesicular lung conducts sound about as well as solid lung. A tube once thrown into sonorous vibrations will transmit sound better to solid than to vesicular lung, for solids transmit to solids better than to aeriform bodies. Solid lung again in vibration will transmit sound to the thoracic walls better than vesicular lung, for solids accept sound better from solids than from aeriform bodies. Although I believe the solid conduction to the surface aids in the audition of bronchnoea sounds, I am of opinion that the abolition of vesicular respiration sound is the great cause of our hearing this acoustic sign. We have seen that vesicular

bruits can eclipse bronchial sounds.

In determining whether tubular bronchial or brochnœa sounds are unhealthy, and may be the result and evidence of phthisis, we are to remember that the locality of the sounds is as essential to the solving of the problem as the sounds themselves. What in one part of the thorax is an unmistakable sign of disease, and that is presumptive of the presence of tubercle and consolidated lung, in another part is perfectly normal and of no account whatever as evidence of disease of any kind. In the interscapular regions bronchial respiration sounds are normal, while, on the other hand, in the supra-clavicular and infra-clavicular regions they are highly morbid and very suggestive of pulmonary consumption. At the scapular regions these sounds are frequently heard, but less so in the first stage of phthisis than in the two following ones, and in simple hepatisation. Here they are abnormal.

When tubular respiration sounds have become established in the first stage of phthisis, they almost invariably remain for some considerable time. It does occasionally happen that these sounds disappear, and are succeeded by a quasi-vesicular sound when the patient is improving; but this occurs chiefly when there has been present some inflammatory consolidation. When softening with moist sounds in abundance occurs, tubular respiration sound frequently becomes inaudible, the former totally masking it.

Sonorous and sibilant Rhonchi. Dry and humid Crackle or Clicking. Humming. Buzzing. Arrowroot Crepitation. Wool or Yarn tearing Sound. Rolling Sound.-Pleural Sounds.-Crepitation, fine and medium.

SONOROUS AND SIBILANT RHONCHI.-It has been usual amongst authors, in treating of pulmonary consumption, to omit rhonchi as signs of phthisis; and if incidentally mentioned, these important and very common sounds in the course of this disease have been referred to rather as evidence of the presence of bronchitis in contra-distinction to phthisis, and even as tolerably good presumptions of the non-phthisical nature of the malady of the patient who has been the subject of them. From my own experience I would say that these sounds have been erroneously estimated. Far from their presence indicating the absence of phthisis and the presence of mere bronchial affections, they are commonly, if not very commonly, the products of the former malady, and may be rendered valuable aids in the detection of this disease, if rightly understood. It is very true that these sounds are much more constant signs of bronchitis than of phthisis; that they are, in short, more the signs of bronchial than of pulmonary disease, in the same way as harsh and deficient vesicular inspiration and coarse long expiration are more the signs of phthisis than of any other disease.

Few examples of phthisis pass through the first stage without the development of these signs. But they differ in several respects from the same signs in mere bronchitis.

The sonorous rhonchus is a small tube sound, the tube being about the size of a goose quill. Its characters seems to indicate a degree of constriction during the passage of air, retarding this fluid, exciting friction, and throwing the tube and air into prolonged musical vibrations. The air seems to pass through the tube at a moderate rate. The constriction or narrowing of the tube depends generally upon congestion and thickening of the mucous membrane, and upon the presence of tenacious mucus in very moderate amount. The sibilant rhonchus is a finer sound; it is of higher pitch, and of shorter duration. It possesses a hissing character. This