it to be dependent upon the greater degree of angularity and curving of the bronchial tubes at the left apex, and to some impediment offered by the presence of the heart on that side.

The mechanism of the harshness of respiration in the early stage of phthisis is due to the increased resistance which the air, drawn into the larger bronchial tubes by the expanding cavity of the chest, has to overcome in the terminal bronchi in passing into the ultimate vesicles, through the presence of surrounding tubercles, and to the resistance offered to the expansion of the cells themselves partially filled, as many of them are, with tubercle corpuscles, and by the presence of surrounding vesicles laden with that material. The friction of air passing along a fine tubule, pressed upon by tuberculated vesicles and agglomerated tubercles, is greater than in the case of a tubule surrounded by soft light aerated vesicles. The vesicles themselves, laden or partially laden with tubercles, will dilate with more resistance than free vesicles, and more noise will be produced; for resistance to motion, to a certain extent, increases sound. Even healthy vesicles will expand with more noise when surrounded by lung rendered even slightly more dense by the presence of tubercle corpuscles, for the resistance will be

increased.

Harshness of respiration sound is due likewise to the greater velocity which marks the passage of a given quantity of air in a narrowed tube. The deficiency in amount and duration of respiration is to be attributed to the smaller amount of vesicular structure that can be inflated. The reason of the respiration being of shorter duration appears to be this: the process of expansion of the cells is early concluded, being comparatively slight in amount. The resistance to the act, though sufficient to produce a harsh quality of sound, is as nothing as yet in the presence of the inspirating forces, and totally unable to protract the vesicular dilatation that is at all possible. The chief impediment to inspiration, in the case of harsh deficient sound, occurs at the termination of the act. It is rather a sudden absolute stop which occurs to the entire act, and not a pause taking place during the progress of the act, to be overcome by increasing force, as in the expiration of phthisis, which may be, and generally is, long. In inspiration, the air is absolutely stopped, can proceed no further, and therefore the bruit too is early suspended, the air not being capable of passing beyond the source of the impediment. In expiration

on the other hand, the impediment is experienced in the course of the discharge, and the air may yet, after the temporary obstacle is overcome, by the accumulating force of the contracting and yet elastic lung, and the collapsing walls of the chest, pass on, and be discharged by the trachea and glottis; the sounds of the expiration of air being continued during the whole movements. In divided and "wavy" inspiration, the impediments operate to produce a pause or abatement during the course of the sound.

The mechanism of the click, or clack, or dry crackle, is this: the fine bronchus or tubule being pressed upon by the superincumbent tubercle, the opposite sides come in contact; these sides adhere the more readily that they are covered with a more than usually adhesive mucous secretion; the advancing column of air drawn along by the increasing expansion of the chest, after perhaps a temporary but almost unappreciable check, breaks asunder the connected sides of the tube, the connecting mucus drawn out into a quasi membrane, suddenly ruptures, the ruptured sides suddenly recoil, the air passes, and the sides of the tubules separate; the result is, that a quick sudden motion is produced by the air overcoming an obstacle, and a noise is caused, which we designate or describe as a click, or clack, crack, or crackle. This noise may be imitated by placing the lips wetted with saliva together, and suddenly separating them.

The humid or moist crackle, which occasionally accompanies harsh respiration, is produced by the breaking or rupture of small bubbles of air, composed of particles of air involved in walls of liquid secretion in the bronchial tubules, or by the passage of air through thin secretion in the same parts. But of moist crepitations and other allied bruits, we have to speak at greater length at a more advanced part of this work, when the less early stages of consumption are brought under notice.

CHAP. III.

FIRST STAGE: AUSCULTATION-continued.

Feeble deficient inspiration Sound. - Diagnosis and Aid from Differential Stethoscope. Healthy respiration Sound may, by comparison with unhealthy harsh Sounds, appear unhealthy.

THE vesicular inspiration instead of being harsh, not infrequently is feeble and little audible in the first stage of phthisis. The feeble respiration sound, of which I now treat appears to me, though feeble, to partake less of the fine divided character proper to vesicular respiration than the harsh breathing sound of which I have just written. It has, according to my experience, occurred at a later stage than harsh respiration sound, or when the deposit of tubercles has been more general in a part and more annihilating, so to speak, of vesicular movement. It is more a negative than a positive alteration of healthy breathing sound. It is frequently more remarkable for the absence of the finely divided rustling healthy respiration bruit, than for any positive quality, to which it is easy to give a name. The term indeterminate, which Skoda so frequently employs, is often happily applicable to the defective or feeble breathing of phthisis. Feeble defective inspiration sound of phthisis is so marked in some cases, as to make itself known as such by the application of the wooden stethoscope to the diseased part only. It is however generally made most manifest to the mind by comparative examination with other parts. But the differential stethoscope, in cases of considerable deficiency, used simultaneously, affords the best evidence. Inspiration sound is audible at healthy parts, and inaudible at the diseased point. The reverse of what occurs in the cases of harsh respiration. It is liable to be mistaken for the natural respiration sound of some persons advanced in life, which is scarcely audible, in persons of calm temperament, of slow circulation and respiration, and who are rather corpulent. In these persons, however, attentive listening will detect an inspiratory bruit, normal in length, although ill pronounced in pitch and intensity. This character of respiration sound is general over both sides of the chest, which is not the case in the feeble respiration of phthisis. The differential stethoscope will, under such circumstances, prove of great utility. The feeble inspiration sound of the first stage of phthisis, may be mistaken for the very deficient inspiration sound of dry old

cavities. I believe this to be a rather common error. The respiration of many cavities which are dry, of no great size, which have free bronchial communication, both intra and extra, with little or no mucus at the openings of the bronchi, to produce bubbling or clicking, free from distinct cavernous pectoriloquy, approaches the character of feeble vesicular respiration. The noise is that simply of air passing along a tube, or in a space free from the somewhat divided, opposed, or rustling character of vesicular respiration. The approach to feeble ill-formed vesicular respiration sound is such, that it may be, and often is, confounded even by practical stethoscopists with the feeble condition of breathing in the first stage. The differential stethoscope under these circumstances proves of some value. Both sound collectors being applied, one on the sound side, and the other on the feeble side, the result is such as to convince the hearer that very different conditions of lung are present at the two parts. If the feeble inspiration sound be proceeding from a dry cavity, the contrast is very great, when the two parts are listened to in succession; such as is scarcely ever obtained in the case of healthy lung, contrasted with phthisical lung in its first stage of degeneration. If the two cup collectors be simultaneously employed, the ear which is connected with the sound lung is the only one which, to the mind, seems to receive any sonorous impression, which is hardly the case when the two ears are listening, one to a healthy lung and the other to a lung the seat of tubercle in its crude or nascent state, and while yet in very moderate amount. The absence of hearing through the ear connected with the diseased side, always indicates some very considerable amount of deposit, or some form of very serious or advanced disease. When silence is not due to a large amount of crude tubercle, it is generally an old dry vomica that is present, but total hepatisation will produce the same result, but this hepatisation of the apex. is extremely rare. Deficiency of inspiration sound, productive of the same result, may be induced by pressure on the chief bronchi, by tumours originating in the mediastinum or root of the lung, by aneurism of the aorta, and by complete filling of the pleural cavity of one side by effusion; but in these comparatively rare cases, the proper signs of these diseases respectively will declare the nature of the malady. I have in a few cases seen cancer of the lung produce such an amount of feebleness of respiration as to cause respiration sound to be obliterated, so to speak, when the sound collectors of the differential stethoscope have been employed

In

simultaneously upon the diseased and healthy parts. these cases too, a stridulous pipe sound served to denote great pressure.

The depression of the ribs, and the inward dragging of the intercostal soft parts, the presence of cavernous pectoriloquy, and the long duration of the disease, will generally suffice, moreover, to indicate that the feeble inspiration sound is that of a cavity. It is ever to be remembered, that the feeble respiration of a lung with a moderate amount of crude tubercle, is very incomplete, compared with the feeble respiration of a cavity, and the expiration, unlike that of many cases of cavities, is never cavernous. Let me be understood: I speak of the feeble respiration of certain cavities only; I am fully aware that the dry respiration of some few cavities, in which much friction with the air takes place, is very loud, and tends to obscure or eclipse the vesicular respiration sound of healthy lung, when the differential stethoscope is employed with its two sound collectors at once. Feeble inspiration sound, in the first stage of phthisis, is for the most part unattended with marked depression of the ribs, or with great loss of curving. The intercostal spaces are not often retracted. The voice may be bronchophonic, with undue vibration and fremitus, but it is never, of course, cavernous, nor does it ever seem to proceed immediately from under the skin simply into the stethoscope. The percussion is often clear, it may be flat, or short and acute, but it is seldom short wooden, or absolutely dull.

In resolving the question, whether a respiration sound which is feeble on one side, compared with the respiration sound on the other side, be morbid, we must bear in mind, that the natural respiration sound may appear weak and deficient, when compared with the unhealthy harsh respiration sound of a diseased part. To decide which is the diseased side, when neither the harshness nor the deficiency is well marked or associated with other signs, is often exceedingly difficult. This difficulty is very considerable, when the loudness or harshness is heard on the left side, where it is not uncommonly normal. It is well not to rely very much upon a slight difference, particularly if the fullness be upon the left.