TEMPERATURE TOPOGRAPHY 685 



in conjunction with a diminished surface temperature, as in the cold 

 stage of ague, might be due either to diminished heat-loss while the 

 heat-production remained normal, or to diminished heat-loss plus 

 increased heat-production. 



The following tables illustrate the differences of temperature found 

 in the body. It should be remembered that the numbers are not 

 strictly comparable with each other ; the temperature of the mammals 

 in which direct observations have been made on the blood is not 

 exactly the same as that of man, the temperature of the dog, for 

 example, being a little (about i C.) higher. Then in the same animal 

 there is no very constant ratio between the temperature of the blood 

 in two vessels or of the skin at two points. Even in the same vessel 

 the temperature may vary with many circumstances, such as the 

 velocity of the stream, and the state of activity of the organ from which 

 it comes. Apart from physiological variations, experimental fallacies 

 sometimes cause a want of constancy, especially in measurements of 

 blood temperature. The insertion of a mercurial thermometer into a 

 vessel is very likely to obstruct the passage of the blood ; and if the 

 blood lingers in a warm organ, it will be heated beyond the normal. 

 In man the blood-temperature in the arteries at the wrist has been 

 estimated indirectly by the calorimetric method of measuring the 

 blood-flow in the hand (p. 122), probably with greater accuracy than 

 would be attainable by the direct insertion of a thermometer, were 

 this permissible. The temperature of the calorimeter is determined at 

 which it neither imparts heat to the blood nor gains heat from the blood. 

 On the assumption that the heat-production of the resting hand is 

 negligible for this purpose,* the temperature so fixed will be that at 

 which the blood enters the hand i.e., the temperature of the arterial 

 blood at the wrint. 



Blood. (Dog.) 



Right heart .... 38-8 C. 

 Left - - - 38-6 



Aorta - - -3 8 '7 



Superior vena cava - - 36-8 



Inferior - 3 8>I 



Crural vein - - - - 37* 2 t 



,, artery - - 38-0 



Profunda femoris vein - 38-2 



Portal vein - 3 8 ~39 1 Varies with activity 



Hepatic vein 38'4-39'7J of digestive organs. 



Arterial blood at wrist in man 0-5 below rectal temperature. 



* Since, of course, some heat is produced in the hand even at rest, although 

 doubtless less per unit of weight than hi the resting body as a whole, the 

 arterial blood temperature as thus determined must be somewhat too high. 

 No error is caused by this in the calculation of the blood-flow in the hand 

 (p. 122) ; for while the factor T T' in the denominator is somewhat too great, 

 thi corresponding quantity of heat produced in the hand is included in H in 

 the numerator. 



t The following numbers were obtained (in an anaesthetized dog whose 

 rectal temperature had fallen 2 C.) for the temperature of the walls of the 

 crural artery and vein, as measured by an electrical resistance thermometer. 



Leg of dog lightly wrapped in wool. "\ 



Crural artery - 34'95 



vein 34-76 I Rectum, 36-2 



Leg more carefully wrapped up. j Air, 16*3 



Crural artery - 34' 7 

 vein 34' 82 J 



