ANIMAL HEAT. 513 



what lower than that of the right. This has been explained on the 

 ground that the right heart is in closer proximity to the warm liver; 

 also, that the blood going to the left heart has been cooled from its 

 passage through the lungs during respiration. 



Estimation of Temperature. Our knowledge as to difference in 

 degree of the heat of the same or different bodies is gained by ther- 

 mometry. Thermometers are instruments for measuring tempera- 

 tures. Their principle is based upon the physical phenomenon of 

 expansion of bodies by heat. Liquids are best suited for this purpose. 

 Mercury and alcohol are the only two liquids used. 



The mercurial thermometer is the one most extensively used. 

 It consists of a capillary glass tube, at the end of which is blown a 

 bulb. Both the bulb and portion of the tube are filled with mercury. 

 The expansion of the mercury is registered by a scale which is grad- 

 uated either upon the stem itself or upon a frame to which it is 

 attached. On the Continent,, and more especially in France, the 

 stem is divided into one hundred parts, or degrees; this division is 

 known as the Centigrade scale. In England, Holland, and North 

 America the Fahrenheit scale is used. Its stem is divided into two 

 hundred and twelve degrees between zero and the boiling-point of 

 water. 



Estimation of Heat. Calorimetry is the measuring of the quan- 

 tity of heat which results from the transformation of energy. By it 

 is learned the amount of heat possessed by any body, and what 

 amount of heat the latter is capable of producing. Calorimetric 

 measurements are expressed in thermal units. A certain quantity of 

 heat with which all other quantities are compared is known as a 

 thermal, or heat, unit. 



A thermal unit is the quantity of heat required to raise a definite 

 quantity of water from one defined temperature to another defined 

 temperature. A particular thermal unit has been called by some 

 authors a Calorie. It is the quantity of heat necessary to raise a 

 kilogram (2.2 pounds) of water 1 C. An English heat unit is the 

 quantity of heat required to elevate one pound of water 1 F. One 

 Calorie equals 3.96 English heat units. In Germany scientists fre- 

 quently use the word calorie, but mean the gram-calorie. It repre- 

 sents the quantity of heat that is required to elevate the tempera- 

 ture of 1 gram of water 1 C. 



The whole science of animal heat is founded upon thermometry 

 and calorimetry, as well as the indirect method of calculating the 

 antity of heat produced from the quantity of nutritive materials 



33 



