4 
462 ANIMAL PHYSIOLOGY, 
tent to which they are such would depend, we should suppose, 
upon the degree to which they were the seat of metabolic pro- 
cesses ; and actual tests establish this fact. Thus, among glands 
the liver is the greatest heat-producer; hence the blood from 
this organ is the warmest of the whole body. The muscles also 
are especially the thermogenic tissue. 
The temperature of the blood in the hepatic vein is warmer 
than that in the portal, a clear evidence that the metabolism of 
this organ has elevated the temperature of the blood flowing 
through it. 
The temperature of the blood (its own metabolism being 
slight) is a pretty fair indication of the resultant effect of the 
production and the loss of heat. 
For obvious reasons, the temperature of different parts of 
the body of man and other animals varies. 
The statements of observers in regard to the temperature of 
various animals and of different parts of the body disagree in a 
way that would be puzzling, were it not known how difficult it 
is to procure perfectly accurate thermometers, not to mention 
individual differences. The axillary temperature is about 
37°5° C.; that of the mouth a little higher, and of the rectum or 
vagina slightly more elevated. The mean temperature of the 
~. blood is placed at 39° C. 
It is a very striking fact, however, that the different parts 
of the body ordinarily accessible by a thermometer vary so 
little—not more perhaps than a degree or a degree and a half. 
The temperature of the hepatic vein has been put down as 39'7°, 
and it contains the warmest blood of the body. 
Comparative —The temperature of various groups of animals 
has been stated to be as follows: Gull, 378°; swallow, 44'03°; 
dolphin, 35°5°; mouse, 41'1°; snakes, 10° to 12°, but higher in large 
_ Specimens (python), Cold- blooded animals have a temperature 
a little higher (léss than 1° C. usually) than the surrounding air. 
_During the swarming of bees the hive temperature may rise 
‘from 32° to 40°. All cold-blooded animals have probably a 
higher temperature in the breeding-season. In our domestic 
mammals the normal temperature is not widely different from 
that of man. 
Variations in the average temperature are dependent on 
numerous causes which may affect either the heat produc- 
, tion or heat loss: 1. Change of climate has a very slight but 
real influence, the temperature being elevated a fraction of 
| a degree when an individual travels from the poles toward 
