the clavicles may be in their lowest position, and not raised and fixed as in severe cases of bronchitis. It will also often occur that this flattening, or falling in, and the lessened breath movement will be less on one side than on the other, indicating generally that the progress of the disease has been greater on one side than on the other; but, in forming this opinion, it will be necessary to consider the relative size of the pectoral muscles of the two sides of the chest, for they commonly differ somewhat, and in persons who employ the right arm in laborious occupations they vary very considerably. It will also frequently be seen that the intercostal spaces do not exhibit their normal fullness, and particularly if the patient be thin; and although this does not usually strike the unpractised eye at first, it is occasionally so marked as to show distinct depressions.

If we now turn to the back aspect of the body, it will be seen that the motion is indistinct, so much so as to require attention to detect it with certainty. It is also common to find a little tendency to roundness of the shoulders, and also to an increase of width between the scapula. The flatness above the transverse process of the scapulæ is also usually evident.

With these various changes it will be noticed that there is no increase in the abdominal movements, nor any unusual expansion of the thorax at its lower part.

When considering these circumstances, it will be readily understood that their due appreciation will depend upon the amount of knowledge which the

M

observer has as to the movements and form of the chest in health,-information which must include not only the average movement in all persons in health, but also the peculiarities of the individual, as to height, width of chest, and sedentary or active habits:—all of which exert a material influence upon the normal amount of chest-movement. It is also requisite to recognise the broad distinction in the chest-movement, which occurs in the sexes. It is well known that in women there is usually much more breath-movement at the upper part of the chest than is found in men; a difference due, doubtless, to the unequal pressure exerted by the stays, which constringe the lower part of the chest, but allow the upper part to act freely. Hence, there may be much diminution in the chestmovement in women, and yet the amount remaining be equal to that which occurs in men; and a reduction to the amount observed in men shows far greater diminution of breath-movement than could be inferred from an equal diminution in men. It is important, therefore, to bear in mind, that small breath motion has very different significance in the two sexes, and as it is normally so much greater in women than in men, the smaller variations are more readily recognised in the former. Hence, in studying this condition of the chest, it is better to select women than men.

To one whose eye has been well trained to appreciate minute changes in the chest-movement, no other test is required, but there are many who seek other means of admeasurement. For this purpose some upon each shoulder, to

place the fingers of the hand

obtain a tolerably fixed point, and then, stretching out their thumbs to various parts of the chest, attempt to measure the amount of motion. This method has but little that is rigorous in it, and would scarcely at all aid the practised eye.

The two instruments which are now commonly used for this purpose are Sibson's and Quain's chest measures, and with either of them a moderate amount of accuracy may be obtained. Sibson's instrument, consists of a metal lever, connected with a pointer and graduated dial, by the intervention of a silk thread and spring. One end of the lever is placed upon the chest, or upon the finger when laid upon the chest, and the dial being held firmly in the hand, the lever moves up and down, and varies the position of the pointer as the movements of the chest vary. It requires much practice to be able to hold the dial so firmly that, on the one hand, no pressure shall be made by it upon the end of the lever which is in contact with the chest; and, on the other, that the contact of the lever and the chest shall always exist; for it will readily be understood that the lever will rise and the pointer move by pressure downwards of the hand, as well as by pressure upwards of the chest; and also that, if the contact be not well sustained, there may be a degree of movement of the chest which will pass unregistered. In the hands of one well practised in its use, as, for example, in those of its inventor,-we cannot doubt the accuracy of the results; but in other hands insufficiently practised, it will as certainly cause

error.

But the least fallacious experimental method is that of measuring the amount of inspired air, and by this, as we have already stated, it may be proved that in the stage of disease now under discussion, there is a marked diminution in the amount of air which is inspired at each inspiration.

It is scarcely necessary to state that the amount of variation in the chest-movement, and in the form of the chest, will be proportioned to the amount of deviation from health, and therefore will vary with each person examined. We affirm that there is a diminution in the breath-movement in every case, and that as time progresses, it increases and leads to other abnormal conditions.

EXPANSIBILITY OF THE LUNGS.

The structure of the lung facilitates expiration but not inspiration.

During the expansion of the chest the capacity of that cavity is increased in all directions at the same time, so that the lung increases in size, both in its perpendicular and transverse diameters; but, as the central part or root of the lung remains fixed, the greater portion of the expansion takes place in front of, above and below the root. The lungs are composed of two principal structures, and it must be by the expansion of one or both of these structures that its enlargement is effected. Of these two there is no evidence to show that the tubular structure has any power of elongation, although, from the arrangement of its muscular fibres, it has a power of contraction and

expansion within very narrow limits around its own axis. Neither is there any evidence of any method whereby the tubular structure may be folded, so that at one time the peripheral extremity of the tube may be more distant from the central tube than at others, although this may probably occur in a small degree. There is also a small amount of movement in the lower part of the trachea and the large bronchi during the movement of the chest, but it is not in the direction of the long axis of the tube, and is only an undulating movement from behind forwards. Hence, it follows that the whole expansion of the lung is due. to the structures of those parts which lie between and at the extremities of the minute bronchial tubes, and which constitute the vesicular structure of the lungs.

Let us, therefore, ask by what mechanical arrangement this vesicular structure is enabled to expand in both uniform and diverse degrees during a long life. The structure of these organs, as commonly described, is that of a basement membrane, having in its walls yellow elastic tissue, lying chiefly in bands, and lined on the surface with tesselated epithelium. There is, therefore, nothing in this structure which will facilitate expansion, and the power by which the expansion is effected must be from without; in the muscles attached to the parieties of the chest, which draw the yielding structures in such directions as will enlarge the capacity of the cavity, and in this act the air enters and fills the newly created space. The structure of the lung offers no aid whatever in this