In addition, Fig. 1 shows the tracing obtained with the capillary electrometer and Einthoven’s corrected curve. The upper and middle records were shown in his paper on the galvanometric registration of the human elektro-kardiogramm published in 1903.
C. Sir Thomas Lewis
In 1911 Sir Thomas Lewis, Einthoven, and others corre¬lated the ECG waves with the contracting heart and noted that the P wave was related to the contraction of the atrium and that the QRS spiky deflection was associated with ventricular contraction.
The Cambridge Scientific Instrument Company made improvements in the size and capabilities and brought out a table model in 1911, one of which was leased to Lewis at the London Hospital. In 1917 Herrick reported the first case in which the electrocardiogram was diagnostic of myocardial infarction. In 1926 a fully portable instrument was marketed.
From 1934 to 1946 improvements in the quality of recordings were due to the immense work and technique of Frank Wilson at the University of Michigan. He had studied with Lewis and had purchased one of the early electrocardiograph machines manufactured by the Cambridge Scientific Instrument Company in 1914. Wilson’s work led to the introduction of the central terminal, the V leads applied to the chest wall, and the leads applied to the limbs which improved the quality of recordings. Goldberger, in 1942, introduced a techni¬que of obtaining augmented unipolar extremity leads, labeled aVR, aVL, and aVF. This allowed a large amplitude deflection to be recorded.

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