CIIARACTEKS OF II^EMATOTIIERMA. 3 



The molecular movements and changes in the organs of vege- 

 tative life constitute a more unintermitting source of caloric. The 

 blood which returns from the extensive seat of such operations 

 aiforded by the mucous intestinal tract is warmer than before it 

 enters that tract : the blood of the hepatic vein after its passage 

 through the portal circulation, and its work in the liver, shows a 

 more marked rise of temperature. Urine in mammals, before its 

 escape, is hotter than blood ; ^ and the rich supply of nerves to the 

 adrenals may relate to the calorific functions of the kidneys. 



The production of heat from the actions of organic life depends 

 on the amount of material for the support of such actions — on the 

 quantity of oxidizable substance introduced as aliment into the 

 body. The greater vigour, activity, waste, or wear and tear, in 

 the warm-blooded machinery necessitate, while they ena])le, a 

 greater energy, and more regular and rapidly recurring perform- 

 ance of the digestive functions ; and the warm-blooded differ from 

 the cold-blooded vertebrates in the greater amount of food which 

 they consume, and the shorter intervals between the times of 

 eating. Warm-blooded animals exemplify this influence; — ^ I 

 weakened,' says Hunter, ' a mouse by fasting, and then intro- 

 duced the ball of the thermometer into its belly : the ball being 

 at the diaphragm, the quicksilver rose to 97° ; in the pelvis to 

 95°, being two degrees colder than in the strong mouse.' ^ The 

 difference of beinsj ^ full ' or ^ fastins^ ' in resistino; cold is a matter 

 of common experience. 



§ 122. Thermogenous Results. — The more active and unremit- 

 ting vital combustion, due to the above-defined advanced con- 

 ditions of the nervous, respiratory, circulating, digestive, and 

 muscular systems, keeps up a constant temperature, as a general 

 rule, in the Hmmatotherma, Avhich is usually so much higher 

 than that of the surrounding medium as to cause the sensation 

 of warmth to the hand touching the body. In man the mean 

 temperature of the interior of the body is 100° Fahr. ; in the dog, 

 101°; in the ox, 100°; in the mouse, 99°; in the whale, 105°. 

 In Birds ^ the mean temperature ranges in different s})ecies from 

 106° to 112°. 



The heat-producing powers in healthy IIcBmatotlterma are more 

 active as the surrounding medium is cooler; and cold, much 

 below freezing, is long resisted, and habitually, by the wann- 



' iir. 100° or 101° Fahr. as against 97° Falir.; (39.5, as against 37 or 30 Cent.) 

 - xciv. p. 145. See also p. IG, for a similar illustration of loss of heat ihrongli 

 starvation in ducks. ■' JV-. 



15 2 



