IT 2 BLOOD AND LYMPH 



blood is therefore the average temperature of the whole 

 body. In man the production of heat and the loss to the 

 outside of the body is so nicely balanced that the average 

 or blood temperature remains almost constant. This 

 being the case, any rise in this temperature indicates a 

 more or less serious disturbance in the body. In some 

 animals, such as the fishes, frogs, and reptiles, the loss of 

 heat is so great compared with the production that the 

 temperature of the blood is only slightly above that of the 

 surrounding air or water. Such animals feel cold to the 

 touch, and are spoken of as cold-blooded animals. They 

 are also called variable temperature animals, since their 

 average temperature varies with that of their surround- 

 ings. In birds and mammals, including man, the amount 

 of heat produced is greater and the loss so nicely balanced 

 that their average temperature is not only kept constant, 

 but at the same time is higher than that of their surround- 

 ings and does not vary with the outside temperature. 

 Such animals feel warm to the touch and are therefore 

 called warm-blooded. 



In man the temperature of a healthy body remains at 

 about 98° Fahrenheit, and though it may increase to 103° 

 or 105° in violent exercise, this is only temporary and it 

 sinks in a few hours to normal. A continued temperature 

 of over 100° is usually an indication of fever. This fact 

 enables the physician to discover at once the presence of 

 fever by taking a person's temperature. In birds the 

 temperature is much higher than in man, these animals 

 having an average temperature of 105° Fahrenheit. 



Summary of blood action. — The blood is usually spoken of as 

 the nutritive fluid of the body, since its main function is to supply 

 food or nourishment to the tissues. It has, however, other func- 



