Was reading on clinical thermometers and what I've noticed is that they say temperature flows from an area of high temperature to an area of lower temperature. Now, the clinical thermometer has a constriction which allows for breaking of the thread due to cooling of the buld and the mercury thread therefore stays in position and lets us read the temperature. My question is, why doesn't the temperature at one end, start to regulate the temperature by flowing towards the bulb and mess with the readings

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