[Illustration: Fig. 33.--Apparatus for estimating the venous blood pressure in man, devised by Drs. Hooker and Eyster. The small figure is the detail of the box B. See explanation in text.] In the apparatus shown in the figure (Fig. 33), Drs. Hooker and Eyster succeeded in making estimations of the venous pressure. The box _B_ is held in position by the tapes _A_, so that the vein is visible through the rectangular opening in the thin rubber covering the bottom. The box is connected with the water manometer _G_, by a rubber tube, from which a T-tube enters the rubber bulb _E_. When the bulb _E_ is compressed between the plates _D_, by the coarse thumbscrew _C_, air is forced into the box _B_, exerting a pressure on the vein lying exposed beneath. This pressure is transmitted directly to the manometer =G=, and may be read off in centimeters of water on the accompanying scale. The veins of the back of the hand are used and there must be no obstruction between them and the heart. The rubber-covered box is accurately and lightly fitted over a vein and pressure made until it is obliterated. By measuring the distance above or below the heart level that the hand was when the observation was made, and subtracting or adding these figures to the manometer reading, we obtain the venous pressure at the heart level. Eyster has modified this instrument so that it is now much simpler to operate. He uses a small glass cup with a flaring edge and a diameter of about 2 cm. This is sealed to the skin directly over a vein on the back of the hand by means of collodion. The stem of the cup has a rubber tube leading to a small hand bulb and to the manometer tube which contains colored water. Slight compression of the hand bulb obliterates the vein which can be seen through the glass cup. The pressure in centimeters of water is then read off. (Fig. 34.) The principle is the same as in the earlier instrument, but the application is easier. [Illustration: Fig. 34.--New venous pressure instrument. (After Eyster.)] Practically Hooker and Eyster found that the normal variation in healthy subjects was from 3 to 10 cm. of water. The pressure rose in cases of decompensated hearts with dyspnea and venous stasis, and returned to normal with improvement in the condition of the patient. It might be possible with this instrument to foretell an oncoming decompensation by the rise in venous pressure. The venous pressure may also be estimated roughly by slowly elevating the arm and noting the instant at which a particular vein collapses. By measuring the height of the vein above the heart some idea may be obtained of the pressure within the right auricle. =The Pulse=