356 Dr Davy on Animal Heat. 



people in all the preceding instances, at the time the obser- 

 vations were made, were sitting by their fireside, as is their 

 usage in the cool climate of Westmorland, the greater part 

 of the year, and all of them, with one exception, seemed to 

 be comfortably warm ; the poorest of them were not in want. 



Old age is commonly represented as cold, and the tempe- 

 rature of the body is commonly supposed to diminish with 

 advancing age. The results of the preceding observations 

 generally are not in accordance with this opinion ; they seem, 

 on the contrary, to shew, that the temperature of old people, 

 at least as regards the deep-seated parts, of which the tongue 

 at its base may be considered as some indication, is rather 

 above than below the average temperature of middle age, 

 taking that to be about 98° of Fahr. Nor, perhaps, is this 

 surprising, when we reflect, that most of the food consumed 

 by old persons — and their appetite generally is good — is pro- 

 bably chiefly employed in administering to the function of 

 respiration, being very partially expended in meeting the 

 waste of the body. 



Probably in very advanced old age, as in very early infancy, 

 the power of resistance to cold is feeble, and the temperature 

 of the body is easily reduced on exposure. An observation 

 which I made, many years ago, in Ceylon, would seem to be 

 confirmatory of this. At seven o'clock in the morning, when 

 the air was 72°, I tried the temperature of an old man, almost 

 a century old, and of a boy about twelve years old, both cool, 

 being thinly clad, and out of doors ; the temperature of the 

 old man under the tongue was 95° ; in the axilla, 93° ; that of 

 the boy under the former, 98° ; and in the latter 96°.5. The 

 observation, too, on the old man in Grasmere, made in Fe- 

 bruary, in cold weather, is also favourable to this conclusion ; 

 whilst those made at the same time, on the other two old per- 

 sons in stronger health, seem to shew, that, provided there is 

 a vigorous action of the heart, and free circulation of the 

 blood, the temperature of the body is easily maintained. 



3. On the Effect of Air of different Temperatures on Animal 



Heat. 

 As from observations made on man on entering the tropics, 



