1893. ANIMAL TEMPERATURE. 217 
these animals find their energy so reduced that they pass the time in 
sleep—they hibernate. 
The higher animals have been classed as the warm-blooded, the 
lower as the cold-blooded. This classification is, however, not 
absolutely exact. Indeed mammals are found, such as the hedgehog, 
bear, and dormouse, which are in an intermediate position, since, in 
spite of their high temperature in warm weather, their temperature 
falls in winter, they become inactive and hibernate, the oxidation of 
their tissues is reduced toa minimum; on the other side, there are 
bees, animals of a low order, which have and maintain a higher 
temperature than most cold-blooded animals, and are not reduced to 
spend the winter in slumber. 
In order that an animal may have under very varying conditions 
a constant temperature, it must possess some regulating mechanism. 
There are two means by which regulation can be obtained, variation 
in the amount of heat produced and variation in the loss of heat. 
Both methods are found in use. When a white mouse, for example, 
is removed from cold to warm surroundings, it regulates its tempera- 
ture by increasing the loss of heat from its body, it sweats and 
exposes to the air as large a surface of its flushed skin as possible ; at 
the same time, its heat-production is lessened, it is less active, it gives 
off less carbonic acid, there is less oxidation in its tissues. Let the 
same animal be now returned to acold chamber. At once its ears 
and face become pale, showing that the vessels of the skin contract, 
and prevent loss of heat by the blood passing to the skin; when not 
in active movement the animal huddles up together, ruffles its fur, 
and makes it as bad a conductor of heat as possible; it also regulates 
the heat production, as shown by involuntary shivers or active volun- 
tary movements, it gives off more carbonic acid, there is increased 
oxidation in its tissues. 
These regulating mechanisms appear to be under the control of 
certain parts of the nervous system. The exact anatomical seat is 
unknown, nor are known the anatomical differences which separate the 
cold-blooded from the warm-blooded animal, and which would explain 
the condition of the intermediate forms, such as the hedgehog, the 
dormouse, bees. It has been shown that by the action of certain 
nervous poisons, and by intense cold, warm-blooded animals may be 
made to pass into a condition somewhat resembling that of the cold- 
blooded animals. Ignorance now reigns here, but not so absolutely 
for ever. 
M. S. PEMBREY. 
