The opinion of the court was delivered by: FORMAN
This is a suit for infringement of letters patent No. 1,821,902, covering a manometer for the measurement of pressure or vacua in fluids, or of differences in pressure or in vacua between several points in fluid systems. More particularly the invention relates to an improvement in so-called sphygmomanometers, or apparatus for the indirect determination of blood pressure. The parties hereto say that the instrument in suit, the mercurial gravity type, has in effect supplanted the aneroid type of instrument, an instrument relying upon the yield or spring of metal for its functioning, because the latter has the defect of losing accuracy in use.
"Measurement of the pulse or blood pressure is a procedure of comparative recent recognition. Its importance was observed in Europe as early as 1828 but it was not until 1876 that the first sphygmomanometer was made in this country, being that of Marey, which for a considerable period of time was used principally in physiological investigations and experiments. The second period began in 1896 with the apparatus of Rivi-Rocci, which consists of an inflatable rubber bag or cuff, 5 centimetres in width, surrounded by a band of firm cloth, which is wound around the arm. To this is attached a rubber tube connected with a reservoir of mercury, from which proceeds an upright glass capillary tube, by the side of which is a wooden scale graduated in millimetres. The rubber bag is placed over the brachial artery above the bend of the elbow, secured by the band wound around the arm and inflated by means of a rubber bulb and tube until the pulse at the wrist has disappeared. As soon as the column of mercury comes to a rest the point on the scale is noted and this is the maximum or systolic pressure. The air in the bag is then gradually released until the pulse clearly reappears and this becomes the minimum or diastolic pressure.
"Many mercurial manometers have been devised since Riva-Rocci's, but they are only modifications of his. Among the mercurial instruments which are worthy of mention and reliable are Cook, Stanton, Janeway and Nicholson."
Or, as Dr. Logan Clendening more entertainingly describes the history of blood pressure in his book, "Behind the Doctor," at page 200, (1933).
"Blood-pressure! Gentle reader, if you have lived to adult life in the twentieth century, you must have heard of that. Somebody in your circle of acquaintances must be either proud or ashamed of his blood-pressure. Yours must be either too high or too low or just right. Gaze reverently, then, on the countenance of the perpetual curate of Teddington, the Reverend Stephen Hales, who invented the blame thing.
"The Reverend Stephen, of course, had none of our modern instruments for measuring this pressure. He used the direct method -- actually observing how high a column of blood would rise in a tube tied into the blood-vessel of an animal.
"The first blood-pressure observations were made in 1910. Afterwards Hales experimented on 'two horses and a fallow Doe.' His first experiment on horses he records thus: 'In December I caused a mare to be tied down alive on her back; she was fourteen hands high, and about fourteen years of age, had a Fistula on her Withers, was neither very lean, nor yet lusty. Having laid open the left crural Artery about three inches from her belly, I inserted into it a brass Pipe, whose bore was one-sixth of an inch in diameter; and to that, by means of another brass Pipe which was fitly adapted to it, I fixed a glass Tube of nearly the same diameter, which was nine feet in Length. Then untying the Ligature on the Artery, the blood rose in the Tube eight feet three inches perpendicular above the level of the left ventricle of the Heart.'
"Following Hales's work the next advance in the study of blood-pressure was the description by Jean Louis Marie Poiseuille, in his graduating dissertation in medicine in 1828, of a haemodynamometer. This instrument measures the pressure by direct insertion of a cannula into the blood-vessel, just as Hales's did, but it substituted a mercury column for the column of blood. Twenty years later, in 1847, Carl Ludwig added a float on the top of the mercury column and caused it to write on a recording cylinder, thus, as Stirling says, giving us at one coup 'the kymograph or wave writer, and the application of the graphic method of physiology.'
"These measurements were all made on animals. The first record of the blood-pressure in man was made in 1856 by Faivre, who did as Stephen Hales did on his mare -- he inserted a tube in the femoral artery of a man during an operation for amputation of the leg, but instead of measuring the height of the column of blood, he read the pressure as recorded on a column of mercury -- it was 120 millimetres, the standard we still use as 'normal' for the systolic pressure.
"Vierordt and Marey about the same time used methods which did not necessitate the exposure of an artery. They were cumbersome, however. Marey's instrument required that the whole arm be immersed in water.
Dr. Theodore C. Janeway, in his book, "The Clinical Study of Blood-Pressure (1907)," in chapter IV entitled, "The Modern Sphygmomanometers," carefully describes a number of instruments beginning with Riva-Rocci's.
William A. Baum engaged in the business of manufacturing manometers in 1916. He incorporated the business under plaintiff's name in 1918. The defendant, which for some years had been engaged in the manufacture of physicians' equipment, such as thermometers, stethoscopes, etc., began making manometers about 1921, for a short time producing the U-type all glass ...