VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS, 203 



for the plastic power of life in varying the process of animal heat, so as to accom- 

 modate it to the external changes, acts for a time with great celerity, though this 

 celerity seems to diminish with the strength. 



Exper. 8. I placed in a large room, where the mercury stood at 36°, 2 slipper 

 baths at the distance of 6 yards from each other. One was filled with cold salt- 

 water of the temperature of 36", the other with water heated to 96°, which was 

 my own heat. Undressing myself in an adjoining room by a fire, I afterwards 

 slipped on a loose flannel dress, and descended slowly into the cold bath, where 

 I remained 2^" ; I ascended slowly into the air, and then sunk myself in the 

 warm bath, where I remained 2™ also : I returned to the cold bath, where I 

 staid 2™ as before, and removed from it again to the warm bath. But during all 

 these changes of media and temperature, the thermometer with its bulb under 

 my tongue never varied from 96°. I attribute this partly to the heat of my body 

 being in some degree defended by the flannel dress, partly to the calm of the air, 

 but chiefly to the slowness of motion in these changes. It may be said that the 

 time of staying in the different baths was not long enough to produce any sensible 

 change in the heat of circulating fluids of such a mass, but this is not consistent 

 with many of the other facts. 



5. The influence of the application of cold water to the surface of the body on 

 the heat, is in some respects regulated by the animal vigour, as the following 

 experiment will show. 



Exper. 9. In the same room I placed a large empty vessel : in this 2 young 

 men sat down in succession, each with the bulb of a thermometer under his 

 tongue. A man standing on a bench with a bucket of cold salt-water containing 

 4 gallons, poured the whole on the head and shoulders, suffering it to run down 

 on the rest of the body. This process took up nearly a minute, during which I 

 examined the mercury, and found it unchanged. They were both directed to 

 continue sitting without motion for a n^inute after, during which, in both in- 

 stances, the mercury rose 2°. A 3d, much inferior in vigour, submitted to the 

 same experiment, and the mercury continued during the affusion of the water 

 unchanged, but in a minute after sunk half a degree. In fevers, where the heat 

 is generally increased from 2 to 6° above the standard of health, pouring a bucket 

 of cold water on the head always reduces the pulse in frequency, and commonly 

 lowers the heat from 2 to 4 or 5°. Of this salutary practice I hope soon to speak 

 at large to the public. 



6. The power of the body in preserving its heat under the impressions of cold, 

 and the changes of temperature, and of media, seems in some measure regulated 

 by the condition of the mind. That fear increases the influence of cold, and of 

 many other noxious powers, will not be doubted ; but the state of the mind to 

 which I allude, is that of vigorous attention to other objects. This, it is well 



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