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A MANUAL OF VETERINARY PHYSIOLOGY 



for the rise in temperature after clipping is by supposing that an 

 actual increase in the production of heat occurs ; this may be 

 due to stimulation of the skin influencing the heat-forming 

 mechanism. Colin clipped a horse on one side of the body, and 

 not on the other ; the subcutaneous temperature in the stable was : 



Clipped Side. 



86-9° F. 



Undipped Side. 



95° F. 



Difference. 



8-1° F. 



The animal was now taken out into cold air at 3 below 

 freezing-point. 



The cooling of the clipped side is very marked, the temperature 

 continuing to fall for three hours, while the slight fall in the 

 temperature of the undipped side was restored to normal in 

 three hours. 



Hibernation.— The effect of a fall in the temperature of the 

 bodies of animals is to produce a depression of metabolism. This 

 is well seen in some mammals, such as the dormouse, which sleep 

 all the winter, during which time they live upon the store of fat 

 laid up in the tissues during the summer. Owing to their 

 depressed metabolism this store is found sufficient to keep them 

 alive, though they wake up at the end of the winter mere 

 skeletons. On waking up the body temperature rises by bounds 

 to the normal, the animal then returning to the condition of an 

 ordinary warm-blooded animal, until the recurrence of the next 

 period of hibernation. As to the causes of this remarkable phe- 

 nomenon we know but little. It is not confined to only one class 

 of animals, since it occurs in mammals, amphibians, reptiles, etc. 

 No purely anatomical differences suffice to explain why some 

 animals hibernate and others do not. External cold is usually 

 assumed offhand to be the initiating factor, assisted possibly by 

 the lessened food supply at the approach of winter. But some 

 other more recondite cause than either of these must exist, since 

 marmots may sometimes hibernate in the summer, dormice will 

 hibernate even if kept warm in the winter ; cold will not neces- 

 sarily cause an animal to hibernate except at the appropriate 



