EXPERIMENTS OF HUNTER. 835 



produced in the height of summer by artificial 

 cold. Whenever the atmosphere falls below the 

 point at which these animals are capable of main- 

 taining their temperature at the normal standard, 

 the circulation through the lungs is diminished, 

 less carbon and hydrogen are given off, and less 

 oxygen is consumed, than during the warmer 

 months. But even in summer, respiration, cir- 

 culation, secretion, nutrition, and their power of 

 locomotion, are much less energetic, than in the 

 higher mammalia. 



It was at one time supposed by John Hunter, 

 that animals might be wholly deprived of life, for 

 indefinite periods of time, by the influence of cold, 

 and be again restored by the gradual application 

 of warmth. With a view of ascertaining the fact, 

 he performed many experiments on the combs of 

 cocks, the ears and feet of rabbits and other ani- 

 mals, which showed that they might be com- 

 pletely frozen, and after wards restored to a healthy 

 state. As might naturally be supposed, the vita- 

 lity of the blood was for the time destroyed, and 

 the capillaries so far weakened, that when the 

 circulation was restored, they were expanded by 

 the vis a tergo, and tumefaction induced, as in all 

 local inflammations. As the natural properties of 

 the blood are in all such cases impaired, it cannot 

 unite with the solids, until renovated in the lungs 

 by respiration ; so that the caloric usually em- 

 ployed in the process of nutrition, is given out in 



