Ammeter and piston pump: what they have in common

1. Step 1. Ammeter — evolved from — Galvanometer. An ammeter is a galvanometer with a scale in amperes and a shunt that carries most of the current.
2. Step 2. Galvanometer — evolved into — Electrocardiograph. Einthoven’s string galvanometer.
3. Step 3. Electrocardiograph — is made of — Silver. The quartz string of Einthoven’s galvanometer is silvered.
4. Step 4. Silver — is material for — Syringe. Early needles were silver.
5. Step 5. Syringe — works like — Piston pump. A syringe is a hand-operated piston pump.

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