A STUDY OF FEVER. 27 



at our command is venesection, and yet, although the dog in 

 Experiment 6 was almost bled to death, the temperature rose 

 from the time the medulla was divided. In Experiment 7 no 

 bleeding of any moment occurred, and the elevation of tempe- 

 rature was therefore more marked than in the first trial. The 

 rise commenced immediately after the division of the medulla, 

 and amounted to almost five degrees, and was still increasing 

 when the animal was killed. As the temperature of the sur- 

 rounding air in both cases was not over seventy, the evidence 

 is conclusive. 



These experiments show very decidedly that fever is entirely 

 independent of the circulation. In the small animal the arte- 

 rial pressure was high, but in the large dog it was reduced to 

 the lowest point compatible with life, and yet, in both instances, 

 tlie temperature rose. Again in neither case was there vaso- 

 motor paralysis, in the first experiment. After division of the 

 par vagum, galvanization of a sensitive nerve was followed by 

 a shght but distinct rise of the arterial pressure. The reason 

 of this rise being so slight was probably the very small amount 

 of blood in the vessels, so that contraction of the latter was 

 not followed by the usual effects. 



In the smaller dog, the evidence that the vaso-motor sj^stem 

 was intact, was unimpeachable. At first galvanization of a 

 sensitive nerve depressed the pressure, very decidedly, on 

 account of the influence of the pain on the par vagum. 



The mere height of the arterial pressure was, however, 

 sufficient to prove the integrity of the vaso-motor system, for 

 if the vessels had all been dilated, the mercury in the tube of 

 the manometer would certainly not have stood over 100. 

 Whenever asphyxia is produced in the normal animal, an 

 enormous rise of arterial pressure results, owing in part to the 

 vaso-motor spasm, which is caused by the excess of carbonic 

 acid in the blood. 



In Experiment 7 this rise of pressure followed the arrest of 

 39 



