604 A MANUAL OF PHYSIOLOGY 



latter method, although subject to obvious limitations, is rapid and 

 free from the danger of conveying infection to the person (Pembrey) . 



The surface temperature is a rough index of the rate of heat-loss ; 

 the internal temperature, of the rate of heat-production. A normal 

 skin temperature and a rising rectal temperature would probably 

 indicate increased production of heat ; an increased rectal tempera- 

 ture, 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, especi- 

 ally 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. 



Llood. (Dog.) 



Right heart - - 38-8 C. 



Left 38-6 



Aorta 387 



Superior vena cava - 36' 8 



Inferior ,, 38*1 



Crural vein 37' 2* 



Crural artery 38 - o 



Profunda femoris vein 38-2 



Portal vein 38-39 / Varies with activity 



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



Tissues. 



Brain 40 



Liver 40 '6-40 '9 

 Subcutaneous tissue 2'i lower 



than that of subjacent muscles 



(man) . 



Anterior chamber of eye - 31*9 ; / 



Vitreous humour - 36*1 \ ^ 



* 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 ' Rectum, 36' 2 



Leg more carefully wrapped up. ("Air, i6'3 



Crural artery - - 34' 7! 



vein 34*82 / 



