stopcock. The object of this glass-encased rubber bulb is to shield the delicate tambour from too sudden changes in pressure. The tambour communicates with the air in the glass bulb outside of the rubber ball, and operating an aluminum needle above the tambour, inscribes its movements on a revolving drum. This makes a tracing upon smoked paper as in the ordinary kymographion. The whole is

FIG. 22.-Erlanger's sphygmomanometer with kymographion in place, showing arm-band and atomizer-bulb inflator.

attached to a metal base and is covered for transportation by a metal case which is somewhat larger than a microscope box and of about the same weight.

The standard cuff is employed and pressure is obtained from a Politzer bag. All rubber tubing is of the highpressure variety to afford rigidity.

The minute details of construction and the operation of

the special stopcock are too extensive to include here, suffice to say that with practice in handling the instrument the readings obtained are accurate and furnish a permanent graphic record of both systolic and diastolic pressures.

Disadvantages.-The chief fault to be found with this apparatus is from the standpoint of clinical availability. Its bulk and weight render it almost useless for clinical work except perhaps in the office or the hospital. The technique of smoking the cylinder and of making necessary adjustments consume more time than can generally be spared during the activities of an extended practice. And in addition the rubber connections and the diaphragm of the tambour often need replacing at most inconvenient times.

The value of graphic records to-day is sufficiently obvious and needs no argument. We would know little of the characteristic temperature curves of malaria or typhoid fever if we depended for our information upon a long column of figures. The course of blood-pressure is equally easy to chart and the curve thus obtained tells us at a glance much that the perusal of the usual written record would fail to convey. In both acute and chronic diseases and during operations the systolic blood-pressure and the pulse should be charted at regular intervals.

This chart is arranged in the form of a combined pulse, temperature and blood-pressure chart, the several scales being so placed that the pulse, temperature and bloodpressure curves do not become superimposed (see Fig. 23).

The chart sheet measures 9 × 12 in., which is the size of the usual hospital history sheet. The chart may be filled in, in different colors if desired to make the record more graphic, but this is not necessary to its accurate keeping.

These charts can be obtained in pads of twenty-five from any surgical instrument dealer at a nominal price.

11. The White Mercury Sphygmomanometer (Fig. 24). -The special sphygmomanometer devised by White is particularly designed to meet the requirements of colleges

and schools, where the demonstration of blood-pressure phenomena is made before a large body of persons. This instrument contains some of the elements of the Faught mercury sphygmomanometer, to which have been added an electrical signal device as shown in Fig. 24. By adjusting

FIG. 24.-Pilling-White Graphic Sphygmomanometer. Designed to demonstrate by electrical contacts actuating colored lamps the excursions of the pulse pressure.

the lamp carriage to the proper position, both the systole and the diastole of the pulse is shown by miniature electrical bulbs. By having the lights of different colors the demonstration is even more graphic and the extent of the oscillation of the pulse wave is shown by the number of lamps illuminated during each cardiac impulse.

CHAPTER V

THE CLINICAL DETERMINATION OF BLOOD-PRESSURE

The Scope of the Test.-The clinical determination of blood-pressure involves an estimation of the systolic and the diastolic pressures, from which may be determined the pulse pressure and the mean pressure. The value of the observation is enhanced if the pulse rate is recorded as a part of this examination.

Any peculiarities noted either while palpating the pulse or in variations from normal in the series of sounds heard during auscultation of the vessel should be recorded. Valuable supplementary information may be developed through a careful consideration of these factors.

For convenience in recording blood-pressure observations the author has devised and now employs the printed card index form shown in Fig. 7, page 59.

Apart from the style of the apparatus there are several methods from which to choose for determining bloodpressure. While any may be employed, there is considerable difference in their accuracy and applicability. It seems advisable when there is choice, to employ that one which has been most amply shown by clinical and experimental evidence to be the most accurate and satisfactory, i.e., the auscultatory. The several methods which may be employed are the following:

The auscultatory.

The palpatory.