Lord Kelvin : Animal Thermostat. 201 



o o 



In 5 minutes the dog was 108, water 112 

 » 6 ., „ 109, „ 112 



„ 11 ., ., 108, „ 112, the respiration having become very 



rapid. 

 „ 13 „ „ 10S, ,, 112, the respiration being still more 



rapid. 

 „ 30 ,, ,, 109, „ 112, the animal then in a very languid 



state. 



" Small quantities of blood being drawn from the 

 femoral artery, and from a contiguous vein, the temperature 

 did not seem to be much increased above the natural standard, 

 and the sensible heat of the former appeared to be nearly 

 the same with that of the latter. 



" In this experiment a remarkable change was produced in 

 the appearance of the venous blood ; for it is well known, 

 that in the natural state, the colour of the venous blood is a 

 dark reel, that of the arterial being light and florid ; but after 

 the animal, in the experiment in question, had been immersed 

 in warm water for half an hour, the veuous blood assumed 

 very nearly the hue of the arterial, and resembled it so much 

 in appearance, that it was difficult to distinguish between 

 them. It is proper to observe, that the animal which was the 

 subject of this experiment, had been previously weakened by 

 losing a considerable quantity of blood a few days before. 

 When the experiment was repeated with dogs which had not 

 suffered a similar evacuation, the change in the colour of the 

 venous blood was more gradual ; but in every instance in 

 which the trial was made, and it was repeated six times, the 

 alteration was so remarkable, that the blood which was taken 

 in the warm bath could readily be distinguished from that 

 which had been taken from the same vein before immersion, 

 by those who were unacquainted with the motives or circum- 

 stances of the experiment. 



" To discover whether a similar change would be produced 

 in the colour of the venous blood in hot air, a dog at 102° 

 was placed in air at 134°. In ten minutes the temperature 

 of the dog was 1011°, that of the air being 130°. In fifteen 

 minutes the dog was 106°, the air 130°. A small quantity 

 of blood was then taken from the jugular vein, the colour of 

 which was sensibly altered, being much lighter than in the 

 natural state. The effect produced by external heat on the 

 colour of the venous blood, seems to confirm the following 

 opinion, which was first suggested by my worthy and ingenious 

 friend Mr. Wilson, of Glasgow. Admitting that the sensible 

 heat of animals depends on the 4 separation of absolute boat 

 from the blood by means of its union with the phlogistic 

 principle in the minute 1 vessels, may there not he a certain 



