instruments, the majority of which were found to be frail, besides requiring special skill to operate, consuming too much time and being above all defective mechanically.

The Standard sphygmomanometer is of the U-tube type and all complicated parts have been either simplified or eliminated. The complete apparatus including the cuff of standard width, and the inflating pump may be enclosed in a mahogany carrying case, measuring 14 X 4 X 41⁄2 in. The lid is hinged and locks in a vertical position to serve as the support of the manometer and the connections. Each arm of the U-tube is provided with a guard cock which remains closed, except during actual use of the instrument, thus preventing absolutely any loss of mercury, excepting with gross carelessness. There are no rubber connections to wear out. The upper nipple to which the pump is attached is provided with a stopcock, which must be closed during the systolic and diastolic readings. The millimeter scale, which can be adjusted to the level of the mercury is reduced one-half to compensate for the fall of the mercury in the other limb, thus the markings give the reading directly in millimeters of mercury. The pressure is obtained by the use of a metallic pump attached to the upper nipple by means of a collapsible rubber tube of special construction, which by its expansion during the operation of the pump, reduces the impact of air before it reaches the mercury in the manometer, and takes the place of the second bulb of the cautery apparatus. An escape valve is provided for gradually lowering pressure during the test.

Disadvantages.-It being perhaps somewhat difficult for one to see the defects in an apparatus of his own

devising, criticisms of this instrument are not here attempted, but are left to others. It is believed that the size of the Standard, and its weight as compared with the more recently devised pocket types of sphygmomanometer, should not be considered detrimental, as many physicians prefer the mercury type, and use it exclusively in physiologic research.

6. The Folding Mercury Sphygmomanometer.-The folding mercury instruments of Cooke and of Janeway, already described, are not at present in great favor, because of the sectional glass tube, which favors the loss of mercury and which is so fragile. These defects have been largely overcome by two surgical instrument makers who, almost simultaneously presented perfected instruments which are in appearance quite similar to each other. One is called the Midget1 (see Fig. 15) and the other known as the Nicholson.2 These instruments follow the design of the Riva-Rocci apparatus, in that they employ the reservoir and vertical-tube manometer. In the Midget instrument, with which I am more familiar, 'the important point is the improved construction in the hinge which serves to join the two segments of the manometer tube, so arranged that the old cone-socket ground-joint connection is abolished, so that, when in position for operation, the two ends of the tube are in close contact, being separated only by a thin washer which prevents the escape of mercury. This arrangement not only reduces the danger of breakage to a minimum but also avoids obstructing

1 Manufactured by George P. Pilling & Son Co., Philadelphia.

2 Manufactured by Precision Thermometer and Instrument Co., Philadelphia.

the view of the mercury column at any point on the scale, highly desirable condition which is not met by earlier jointed instruments. The apparatus is placed in the operative position simply by opening the lid which locks when vertical. The tube with its scale is then unfolded and pressed vertically upward until a spring-catch maintains it

FIG. 15.-Folding mercury sphygmomanometer in operative position, showing details of construction and attachment to arm.

in this position. After use a lever arrangement releases this lock and permits of folding, which movement automatically closes the mouth of the proximal tube. The scale, while being a separate unit and adjustable vertically to accommodate changes in the mercury level, nevertheless follows the manometer tube in all positions. The apparatus

registers up to 260 mm. and when folded is self-contained in a mahogany case measuring 7 X 2% X 15%. The apparatus employs the standard flexible cuff and is inflated by a small hand-pump.

7. The Kercher Mercury Sphygmomanometer.—This little instrument is another modification of the cistern-tube type of apparatus and was suggested in 1910 by Delno E. Kercher,1 is supported on a wooden base and is composed of a small glass cistern containing the mercury and an upright manometer tube reading to 300 mm. The instrument is provided with a pneumatic cuff of 4 X 36 in. and is actuated by a rubber bulb with double valve, provided with a Tconnection for attachment of the arm-band and manometer.

8. The Aneroid Sphygmomanometer. This type of apparatus has much to recommend it and should, if the physician is supplied with an accurate model, be most satisfactory for all purposes, as the present methods of pressure reading do not depend upon the oscillation of the mercury column.

The term aneroid is a misnomer and should never have been applied, but, as it has become so firmly associated with this apparatus, it probably will remain. Aneroid signifies the absence of air, i.e., the presence of a vacuum, yet there is no vacuum chamber in this sphygmomanometer, or in any as far as I know.

The vital portion of these instruments, or the part which actuates the indicator, consists of a group of metallic chambers, made of a special alloy of paper thinness, which when exposed appears not unlike the aneroid portion of the well-known barometer.

Concerning the mechanism of this type of sphygmo

1 Jour. A. M. A., Apr. 2, 1910, Vol. liv, 14, p. 1136.

manometer close examination reveals radical differences in the mechanism of instruments belonging to this class. References to Figs. 16 and 17 show diagrammatically

FIG. 16.-Diagrammatic representation of internal construction of Faught pocket sphygmomanometer. Note the four compression chambers which are intercommunicating one with the other and with the atmosphere through the body of the instrument; also the two nipples, through which the compressing force is directed upon the outside of the chambers causing their collapse, thereby actuating the vertical rod which extending upward connects with the gears as shown.

this difference. Fig. 16 which is an enlarged transverse section of a Faught pocket sphygmomanometer as compared with Fig. 17 shows that in the author's instrument,