EFFECTS OF AGE. 253 



ducting power, defend it for a time from the full action of 

 the external heat. 



It remains to notice certain conditions by which the pro- 

 duction of heat is modified. 



The effects of age are noticeable. M. Edwards found the 

 power of generating heat to be less in old people ; and the 

 same was observed by Dr. Davy, who, in eight people, 

 between eighty-seven and ninety-five years old, found that, 

 although the average temperature of the body was not 

 lower than that of younger persons, yet the power of 

 resisting cold was less in them exposure to a low tem- 

 perature causing a greater reduction of heat than in young 

 persons. 



The same rapid diminution of temperature was observed 

 by M. Edwards in the new-born young of most carnivorous 

 and rodent animals when they were removed from the 

 parent, the temperature of the atmosphere being between 

 50 and 53! F. ; whereas, while lying close to the body of 

 the mother, their temperature was only 2 or 3 degrees 

 lower than hers. The same law applies to the young of 

 birds. Young sparrows, a week after they were hatched, 

 had a temperature of 95 to 97, while in the nest; but 

 when taken from it, their temperature fell in one hour to 

 66^, the temperature of the atmosphere being at the time 

 62^. It appears from his investigations, that in respect 

 of the power of generating heat, some Mammalia are born 

 in a less developed condition than others ; and that the 

 young of dogs, cats, and rabbits, for example, are inferior 

 to the young of those animals which are not born blind. 

 The need of external warmth to keep up the temperature 

 of new-born children is well known ; the researches of M. 

 Edwards show, that the want of it is, as Hunter suggested, 

 a much more frequent cause of death in new-born children 

 than is generally supposed, and furnish a strong argument 

 against the idea, that children, by early exposure to cold, 

 can soon be hardened into resisting its injurious influence. 



