19.) The diastolic pressure is more easily read on the "Tycos." It is where the maximum oscillation of the needle occurs as the pressure is slowly released from the cuff. Although it does not appear that this instrument, if properly made and standardized, could become inaccurate, nevertheless it is advisable to check it every few months against a known accurate mercury manometer instrument. [Illustration: Fig. 19.--Detail of the dial in the "Tycos" instrument.] [Illustration: Fig. 20.--Faught dial instrument.] [Illustration: Fig. 21.--Detail of the dial of the Faught instrument.] Another perfectly satisfactory dial instrument is the Faught (Figs. 20 and 21). The general plan of this differs in some minor points from the "Tycos." I have compared the two and have found no difference in the readings. Both can be recommended. [Illustration: Fig. 22.--The Sanborn instrument.] One or two other cheaper dial instruments are on the market. The Sanborn seems to be quite satisfactory. (Fig. 22.) It is cheaper than the other dial instruments. There is this much to be said, no instrument using a spring as resistance to measure pressure can be recommended. =Technic= The same technic applies to all the mercury instruments. The patient sits or lies down comfortably. The right or left arm is bared to the shoulder, the cuff is then slipped over the hand to the upper arm. (See Fig. 23.) At least an inch of bare arm should show between the lower end of the cuff and the bend of the elbow. The rubber is adjusted so that the actual pressure from the bag is against the inner side of the arm. The straps are tightened, care being taken not to compress the veins. The upper part of the cuff should fit more snugly than the lower part. The part of the instrument carrying the mercury column is now placed on a level surface; the two arms of the mercury in the tube must be even, and at _0_ on the scale. With the fingers of one hand on the radial pulse, the bag is compressed until the pulse is no longer felt. (See Fig. 24.) One should raise the pressure from 10-12 mm. above this, and close the stopcock between the bulb and the mercury tube. In a good instrument the column should not fall. If it does there is a leak of air in the system of tubing and arm bag. Now with the finger on the pulse, or where the pulse was last felt, gradually allow air to escape by turning the stopcock so that the column of mercury falls about 2 mm. (one division on the scale) for every heart beat or two. One must not allow the column of mercury to descend too slowly as it is uncomfortable for the patient and introduces a psychic element of annoyance which affects the blood pressure. On the other hand, the pressure must not be released too rapidly, else one runs over the points of systolic and diastolic pressure and the readings are grossly inaccurate. It is impossible to say how rapidly the mercury must fall. Every operator must find that out for himself by practice. The first