Another condition which counteracts the tendency of simple tubercular deposit of moderate extent to produce increased thoracic voice, is the presence of liquid, such as thin mucus, blood, or purulent secretion in the bronchi. This serves very effectually to reduce thoracic voice. Unless the undulations of the air break down the partitions of liquid, the voice is interrupted. Would we ascertain by experiment how much sound transmitted by air through an air tube, is impeded by the presence of even a very little liquid, let us place even so small a quantity as one drop of water in an indiarubber hearing tube, or a flexible stethoscope, so that at some one very little spot the entire calibre of the tube may be occupied by it, and we shall find that sounds previously heard in force, are now heard very feebly and indistinctly. We can thus understand how it is that, in phthisis, the thoracic voice may now be augmented and now reduced. The liquid comes and

goes.

Before concluding my observations on the mechanism of the alterations in the thoracic voice of the first stage of phthisis, I am desirous of adding the results of my experiments upon the comparative sound-conducting properties of natural lung, and lung abnormally altered in density.

The amount of sound-conducting power of the lung is of itself not sufficient to explain the greater or lesser degree of thoracic voice. Conduction, although an element in the process, is not the only one. The amount of the sound that is to be operated upon by conduction is to be considered, and we have already found that the condition of the lungs and the bronchial passages is very operative in this respect. The consonance due to increased density of the lung greatly increases the amount of sound that may be conducted.

If we have an absolute increase of sound by means of consonance, we may have an increase of thoracic voice, although the conducting power of the lung remains the same. The absolute increase of sound is great element in the increased thoracic voice.

From numerous experiments which I have made, I have satisfied myself of several facts much in accordance with the statements of Skoda.

Sounds communicated from solid bodies, such as a watch, or a table in sonorous undulations from contact with a tuning fork or a musical box, to healthy vesicular lung, are well conducted to the ear directly applied to it; not in an inferior degree than when solid tuberculated lung and cancer lung are employed.

When air stethoscopes, such as my differential stethoscope, are employed, vesicular lung transmits sound from solid bodies much better than when the solid stethoscope is the hearing instrument in use.

When the instrument employed is the solid wooden stethoscope, solidified lung transmits sound rather better than the air stethoscope.

Very dense, tough lung, such as cancer lung, transmits sound even to a wooden stethoscope less perfectly than lung having a little air contained within it. This fact coincides perfectly with what we have stated as to the superiority of hollow wood over solid and hard wood. It also It also corresponds with the fact which I have ascertained, that dense bodies pierced with holes conduct sound better than when entire; and also with the fact that freedom for motion is promotive of the same result.

Lung in a state of high emphysema conducts sound both to the wooden and the air stethoscope worse than healthy vesicular lung. This corresponds with the principle that gasiform bodies have little momentum, and transmit sound with comparative difficulty to solid bodies.

On the whole, I regard the varying degrees of sound-conducting power in the moderate alterations of the lung, in respect of density, as little operative in the modifications of the thoracic voice which we observe in the first stage of phthisis. I agree with Skoda that it is to consonance, due to the unwonted retention of the sonorous undulations of the laryngeal voice, that most of the result is to be attributed.

The bronchophony of phthisis, in its first stage, must be distinguished from sounds bearing a close resemblance to it, almost identical with it, and which are heard in very different morbid conditions of the lung and bronchial tubes.

A. The bronchophony of phthisis is liable to be mistaken for the same sound in hepatisation. When this sign occurs in conjunction with recent hepatisation, we have the remains of small moist crepitation, and when associated with old hepatisation, the absence of respiration is great compared with the diminution in phthisis in its first stage. In hepatisation the advent of disease is sudden compared with phthisis: the acute symptoms have been sharper and have been of shorter duration, lasting in general only a few days, and have embraced pain, shortness of breath, glutinous transparent, almost colourless, or very slightly rusty-coloured sputum. seat of bronchophony in hepatisation is commonly different from that of phthisis. While it is found in the sub-cla

The

vicular regions in phthisis most commonly, in hepatisation it is almost invariably found at the scapular and infra-scapular regions.

B. The bronchophony of phthisis may be mistaken for the bronchophony of dilated bronchi in chronic bronchitis. But this sign, the associate of chronic bronchitis, is usually accompanied with percussion that is resonant, clear, and of long duration. The sibilus, the snoring and cooing bruits, both with inspiration and expiration, attend bronchitis, and comparatively rarely phthisis. The seat of bronchophony, the associate of bronchitis, is more general than that of phthisis; it is commonly found on both sides of the chest. It is more generally heard at the angle of the scapula than in phthisis. I have generally remarked that the thoracic voice of bronchitis becomes more superficial than that of phthisis in its first stage, both at the anterior and superior parts of the chest, and below the angles of the scapula, and that it is less strong, accompanied by less vibration of the wooden stethoscope.

C. The bronchophony of phthisis is to be distinguished from the pectoriloquy proceeding from a cavity. The pectoriloquy of a cavity usually presents characters in itself which serve to distinguish it from the former sign. The voice is usually clear, distinct, and the letters of each word seem to be distinctly articulated, and so conveyed into the ear of the hearer. When the cavity is large, the voice is, as it were, puffed by a large volume of air into the ear: the air seems to pass into the ear, and without much forcible vibration of the wooden stethoscope, unless the voice be very powerful. Whispered voice is heard with the same characters. If moist, the cavity presents large gurglings. If dry, a crack of a resounding or metallic character is occasionally heard as a bubble bursts in the interior. Blowing bruits, as of air entering or escaping from a chamber by means of a bronchial tube, narrow or rough, are occasionally heard. These blowing sounds chiefly hold during expiration. Then "sawing and creaking" bruits, as if coming from a cavity, are likewise heard. These signs serve to distinguish, with much facility, the thoracic voice of a large cavity from that of phthisis in its first stage. The thoracic voice, proceeding from a small cavity covered by consolidated tubercular lung, is more difficult to distinguish from the thoracic voice of the first stage of phthisis. Yet, with attention, this may usually be done. The voice, if the cavity be small, is usually accompanied with more vibration

of the stethoscope than that of large cavities, and therefore more closely resembles the voice of early phthisis. But it is commonly accompanied, if not by gurgling, by large liquid crepitation, which we never have in phthisis in its first stage, unless complicated with a very unusual amount of bronchitis and bronchial secretion. The dullness of percussion, when we have small cavities, not in the first days of their existence, with superincumbent lung, is generally decided, and there is a depression of the chest, and also a deficiency of motion, not commonly found in phthisis with mere crude tubercle.

D. We have the thoracic voice, called bronchophony, in oedema of the lungs ; but the seat of this is the infra-scapular and inferior dorsal regions. It is always accompanied with large liquid crepitation, and the percussion note at the anterior and superior thoracic regions is not abnormally dull. The absence of phthisical sputa, and the presence of unusual dyspnoea, without great emaciation, are remarked in cedema.

E. The same thoracic voice is occasionally heard under the clavicle in cases of empyema as occurs in the first stage of phthisis; but no difficulty attends the diagnosis, as the percussion in the former disease is generally clear below the clavicles, and exceedingly dull, or absolutely so, below the scapula. The respiration sounds are exceedingly feeble and distant, if heard at all at the base of the affected side, and the vocal fremitus is entirely absent below in examples of empyema attended with the bronchophonic voice.

F. The bronchophonic sign of phthisis is occasionally simulated in examples of tumour in the thorax. Aneurism of the commencing aorta, when it compresses the bronchi near the bifurcation, is occasionally attended with considerable increase of voice and fremitus: but the pulsation, the murmurs, the disordered impulse, the great dyspnoea, and the dropsy, and the comparatively advanced age of the patient, will generally serve as the grounds for an easy and decisive diagnosis. Mediastinal tumours pressing upon the bronchi give rise in the same way to bronchophony in the sub-clavicular regions. The voice is increased above and reduced below the spot of compression. Dullness of percussion at the sternum, difficulty of breathing, loud blowing tubular respiration sounds, occasional prominence, and the presence of signs of pressure on the great vessels and on the oesophagus and bronchi, serve to distinguish the bronchophony arising from these causes from the laterally diffused bronchophony of the first stage of phthisis.

VOCAL FREMITUS.

63

CHAP. X.

FIRST STAGE-continued.

Thoracic vocal Fremitus.-Increased in Phthisis.-Sometimes found on the healthy Side of the Chest.--Sometimes reduced in Phthisis.-Not always associated with increased Voice.-Method of Detection.

FREMITUS. The fremitus or vibration of the thoracic walls under the influence of the voice, as learnt by the touch and by the wooden stethoscope, is materially altered in phthisis, and in its first stage, though perhaps to a less extent than in the other three stages. For the most part the alteration is one of increase; but it not unfrequently occurs, as my experience has taught me, that the change is one of decrease or diminution. No sensible alteration of the vocal fremitus is perceived in phthisis, until a very considerable amount of tubercular deposit has taken place. The deposit must be of that extent that will suffice to produce increased vocal resonance, and to give a sensible increase to the weight and resistance of the diseased lung. I should be disposed to say, in the absence of precise actual observations and experiment, that the vocal resonance is usually more early increased to a sensible and reliable extent than the vocal fremitus. I believe a smaller amount of deposit will produce increased vocal resonance than will suffice to cause a sensible increase of vocal fremitus. But as soon as vocal resonance is materially increased, it usually happens that the vocal fremitus begins to augment, and in most examples of disease, though not in all, these two phenomena, viz. increased vocal resonance and increased vocal fremitus, are found to be associated. The increased resonance of the air in the bronchial passages causes the lung to vibrate, and the vibrations of the lung are communicated to the ribs, the intercostal muscles, and the superincumbent soft parts, sufficiently to be perceived by the hand, or to be conveyed to the concha of the ear and the side of the head by means of the solid stethoscope. Absolutely increased and comparatively full vocal fremitus is frequently found upon the healthy side of the chest, when the other side is very considerably advanced in tubercular disease. When by means of great and bronchi-compressing deposit, as well as by extensive expectoration of lung tissue and the free contraction of the walls of cavities, and of the surrounding structure, gene