measure, Dr. Hare's and Mr. Henry Thompson's double tape measures; Dr. Sibson's chest-measurer, Dr. Quain's stethometer, and my own sphygmoscope or pneumatoscope.

Of the common tape measure nothing need be said explanatory of its construction. But the mode of applying it deserves a word or two. The expansive movement outwards of the ribs of one side being the subject of exploration, the tape measure is to be fixed by one extremity upon the spinous process of a vertebra, about the level of the nipple. When the act of expiration is completed, the measure is quickly passed round the side to a point at the middle of the sternum. The patient being now desired to fill his chest, or to "draw a long breath," the tape at the sternum is slackened, and the part which had been placed at that point is permitted to be dragged from it: the amount of dragging is the measure of the expansion of the side. If we desire to compare the expansion of one side with that of the other side, we repeat this process on the other side, and compare the two amounts of dragging.

Dr. Hare's tape measure is a double one, and a very useful instrument it is. I have constantly employed it. It may, like my stethoscope, be called a differential instrument, for it indicates differences very fully. It consists of a tape with the inches numbered, and beginning from the middle. The figures pass to the right and to the left. The middle point, or zero, is generally placed over a spinous process of a vertebra, as in the case of the employment of the common tape measure, and the two ends are brought round the two sides respectively to a point at the middle of the sternum. The exact measure is taken at the end of expiration, and this being noted, and the patient now having drawn a deep breath, the extremities are allowed to drag, and the fresh measurements are taken. We now compare the amount of dragging on one side with that upon the other. The point at which the middle of the differential tape measure of Dr. Hare shall be fixed need not be the spine. If it suits the views of the physician, the starting-point may be made the middle of the sternum. By middle of the sternum I do not mean the point between the top and bottom, but a point equidistant from its lateral borders.

Mr. Henry Thompson's tape measure is much the same as the above, but it is provided with a little saddle to fit upon the spine, and a middle plate to be fixed upon the sternum. The ends of the measure are passed through this. This fixed point aids in marking the amount of dragging.

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DR. SIBSON'S CHEST MEASURER.-This instrument, the first of the kind, is useful when we desire to compare with exactitude the degree of elevation of different parts of the thorax. It is extremely delicate, and in comparative mensuration

it affords results highly satisfactory, both for present purposes and for comparison with future observations on the same patients. In shape and size this instrument resembles a watch. It is supplied with a rack, which is movable. When this rack is moved by the elevation of the chest, an index travels upon a dial on the face of the watch-like instrument, and the degree of motion of the chest is thus indicated. The revolution of the index represents the motion of the chest to be an inch, and the dial being divided into one hundred parts the one hundredth part of an inch movement may be obtained and registered. This instrument is brought in contact with the chest only by its rack or bar. The rack may rest upon the finger placed upon the chest. The hand holding the instrument must be fixed. Localized movements are well suited for observation with this instrument.

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CHEST MEASURER AND STETHOMETER.

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Through the kindness of Dr. Sibson I am enabled to illustrate this subject by the accompanying wood-cuts, exhibiting the instrument and its application to the chest. See vol. xxxi. of "Medico-Chirurgical Transactions."

DR. QUAIN'S STETHOMETER. -Dr. Quain's stethometer is delicate and easily managed. It, too, resembles a watch, having a dial and index. The index is moved by a silk thread, instead of a rack or bar, as in Dr. Sibson's instrument. The silk cord proceeds from the side of the watch-like instrument, and is extended over the part of the chest to be measured. The instrument is laid flat upon the chest, and the silk is held at the further extremity of the part whose motion. is to be taken. The silk cord, during the expansion and swelling of the chest, is dragged upon an axle in the instrument, and the index connected with the axle denotes the mount of dragging. This instrument possesses the great advantage, that while it is applicable to strictly local and restricted movements, it is suitable for measuring the expansion

of an entire side. Thus, the dial being placed upon the sternum, the silk cord may be made to pass over the chest to the spine. An inspiration after a forced expiration will give

upon the dial the amount of motion of the side. This process. repeated on the other side will accurately afford the means of comparing the expansion of the two sides of the chest. For application to circumscribed spots a foot is employed. This rests upon the part examined. For a clever

Foot of Stethometer.

and full account of this instrument and of its capabilities I refer to a paper by the inventor contained in the "London Journal of Medicine."

The hydrostatic pneumatoscope, as my sphygmoscope may be styled, when applied in the measurement of the respiratory movements, indicates remarkably well the rise and fall of the chest during the acts of respiration. It consists, so to speak, of a small projecting mamma of water. The liquid is confined in a cup made of glass or other solid material, like

the body-piece of the wooden stethoscope, and covered over at its mouth with an impermeable membrane of india-rubber, or some such material. To the narrow extremity of the stethoscope-end-like cup a few inches of india-rubber tube is fitted, and to this again a graduated glass tube is attached, having a bore of about one-sixth part of an inch. This glass tube is kept in an erect, or nearly an erect, position. The cup containing liquid is made to occupy a horizontal position by being fitted into a wooden frame, and the glass tube is retained in situ by the same means. The cup is made so as to move slightly, in order to fit the form of the chest in a convenient manner. The liquid is supplied so as to fill the cup, and to rise in the tube a little above the level of the cup. By means of the pressure thus obtained, the membrane at the mouth of the cup and the water form a projecting mamma, sensible to the slightest touch. I find that the mamma is much better formed by employing common indiarubber membrane than vulcanized material, for it gives way more under the hydrostatic pressure. The stand, which must be heavy, say, loaded with lead,-is placed upon a table, and the cup is made to touch the patient's chest when he has expired fully. An act of inspiration is now to be slowly and fully made. The liquid rises in the tube, and the number of degrees travelled over indicate the amount of thoracic elevation and advancement. When one side of the chest has been examined, the other is to be proceeded with. Great care is required to observe similar conditions in respect of both sides. The relative position of the patient and the instrument should be exactly alike on both sides. The instrument must touch the chest to the same extent and in the before the observation of the rise, during inspiration, is same direction, and the chest must have expired fully taken.

This instrument applied over the sub-clavicular region of a patient affected with deficiency of respiration, in the first stage of phthisis, will indicate a deficient movement. When deficiency of sound has been ill-denoted by the wooden. stethoscope, I have occasionally found deficiency of motion by means of this instrument. But in respect of diagnosing early phthisis, the differential stethoscope is much more valuable than the pneumatoscope. Nevertheless, it seems right to refer to every reasonable mode of investigation. I would by no means recommend this instrument in the ordinary examinations of patients; but unless we know something of it we shall not be able to employ it in exceptional