<P> Most implants contain three elements: a' chip' or integrated circuit; a coil inductor, possibly with a ferrite core; and a capacitor . The chip contains unique identification data and electronic circuits to encode that information . The coil acts as the secondary winding of a transformer, receiving power inductively coupled to it from the scanner . The coil and capacitor together form a resonant LC circuit tuned to the frequency of the scanner's oscillating magnetic field to produce power for the chip . The chip then transmits its data back through the coil to the scanner . </P> <P> These components are encased in biocompatible soda lime or borosilicate glass and hermetically sealed . Datamars has also started selling polymer microchips that are being implanted in pets. . </P> <P> In dogs and cats, chips are usually inserted below the skin at the back of the neck between the shoulder blades on the dorsal midline . According to one reference, continental European pets get the implant in the left side of the neck . The chip can often be felt under the skin . Thin layers of connective tissue form around the implant and hold it in place . </P> <P> Horses are microchipped on the left side of the neck, halfway between the poll and withers and approximately one inch below the midline of the mane, into the nuchal ligament . </P>

Where does a microchip go on a dog