Temperature dynamics of the fertile chicken egg

Two thermistor temperature probes were mounted in fertile chicken eggs, one at the position normally occupied by an early embryo and the other in the center of the yolk. Temperature changes were constantly monitored while the eggs were removed from holding refrigerator to incubator, incubator to room temperature, or room temperature to incubator. Computer analysis was used to develop a mathematical model of heat fluxes in the egg. Graphs derived from this model are presented which permit any investigator to predict approximate time and temperature variables under conditions commonly encountered when using the chicken egg in biological research. We found that when the egg is moved from an incubator (38 degrees C) to laboratory bench (25 degrees C), there was a very rapid initial heat loss (over 8 degrees C in 10 min) at a site in the egg which would be occupied by an early embryo. Conversely, when the egg is moved from the bench back to the incubator, nearly 2 h is required for the egg to recover 90% of the heat that it had lost while cooling to 25 degrees C.