Dog 60 70 to 140 70 to 140 101 95 to 110 Monkey 90 30 to 140 30 to 140 101 95 to 108 Horse 80 20 to 120 20 to 120 99 95 to 105 Fowl 80 20 to 140 20 to 140 107 100 to 115 Newly hatched chick 90 70 to 100 40 to 120 108 100 to 115 Fertile egg at start of incubation 103 32 to 110 31 to 125 103 31 to 125 Egg incubated three days 103 98 to 105 80 to 118 103 95 to 118 Egg incubated eighteen days 103 75 to 105 50 to 118 106 98 to 116 This table shows, among other things, that we are considering in the chick not a new proposition to which the laws of general animal life do not apply, but merely a young animal during the process of growth to a point where its internal mechanism for heat control, has power to maintain the body temperature through a greater range of external temperature change. In the cooling process that occurs after laying the living cells of the egg become dormant, and like a hibernating animal, the actual internal temperature can be subjected to a much greater range than when the animal is active. After incubation begins and cell activity returns, and especially after blood forms and circulation commences, the temperature of the chick becomes subject to about the same internal range as with other warm blooded animals. In the case of fully formed animals, the internal temperature is regulated by a double process. If the external temperature be lowered, more food substance is combined with oxygen to keep up the warmth of the body, while, if the external temperature be raised, the body temperature is kept low by the cooling effects of evaporation. This occurs in mammals chiefly by sweating. Birds do not sweat, but the same effect is brought about by increased breathing. Now, the chick gradually develops the heat producing function during incubation, until towards the close of the period it can take care of itself fairly well in case of lowered external temperature. The power to cool the body by breathing is not, however, granted to the unhatched chick, and for this reason the incubating egg cannot stand excess of heat as well as lack of it. The practical points to be remembered from the above are: First: Before incubation begins, eggs may be subjected to any temperature that will not physically or chemically injure the substance. Second: During the first few days of the hatch, eggs have no appreciable power of heat formation and the external temperature for any considerable period of time can safely vary only within the range of temperature at which the physiological process may be carried on. Third: As the chick develops it needs less careful guarding against cooling, and must still be guarded against over-heating.