A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . ve of contractionpasses over a muscle, that portion of the muscle whichis actively contracting is electrically negative to allother parts of the muscle. It is the object of electro-cardiography to detect those differences of electricalEotential which occur during the contraction of theeart muscle and to record them graphically. Thishas been made possible clinically by the genius ofProfessor Einthoven of Leyden, to whom we areindebted for the construction of a wonde
A reference handbook of the medical sciences, embracing the entire range of scientific and practical medicine and allied science . ve of contractionpasses over a muscle, that portion of the muscle whichis actively contracting is electrically negative to allother parts of the muscle. It is the object of electro-cardiography to detect those differences of electricalEotential which occur during the contraction of theeart muscle and to record them graphically. Thishas been made possible clinically by the genius ofProfessor Einthoven of Leyden, to whom we areindebted for the construction of a wonderfully deli-cate galvanometer known as Einthovens String Gal-vanometer. This instrument consists of a powerfulelectromagnet activated by a storage battery of fiveto six amperes furnishing about ten volts. Between 654 REFERENCE HANDBOOK OF THE MEDICAL SCIENCES CardloKraphy (he poles of tliis electromagnet is stretched a delicatefilament of platinum or of silvered quartz; the di-amotor of one of these threads is from two to fourmicrons (about half the diameter of a red blood-corpuscle) and their resistance is about 5,000 Fig. 1236.—Einthovens String Galvanometer. G, Galvanometer: L. arlight; A and B, systems of plug rheostats. (Arthur H. Thomas Company.) When a current of electricitj- passes througli thisstring, at right angles to the lines of force of the mag-netic field of the electromagnet, the string is de-flected to one side or the other according to thedirection in which the current passes. An arc light connection with a rheostat is so arranged that theoperator may send any desired fraction of this cur-rent through the string in either direction and thusdetermine the sensitiveness of the instrument at anyparticular moment. The tension of the string may beincreased or diminished at will bv means ofa micrometer screw, thus readify varyingits sensitiveness. The string is usually ad-justed so that the passage of one milivolt \of current causes a deflection of the shado
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Keywords: ., bookauthorbuckalbe, bookcentury1900, bookdecade1910, bookyear1913
