RESEARCHES UPON FEVER, 423 



the clianges of the circulation, which is at times able to overcome the 

 iuliueuce of these changes. This would seem to be rendered certain by 

 the effects of section above the medulla, which was found to increase 

 extraordinarily the production of the animal heat, the evolution not 

 being notably aftected. In one or more of the experiments the animal 

 lived for twenty-four hours, and at the end of that time, notwithstanding 

 no food had been ingested, the rate of heat production was still notably 

 above normal. Where a result of nerve section remains for twenty-four 

 hours it is usually considered paralytic, and it seems to me only the 

 strongest arguments could establish that the increase of heat produc- 

 tion just mentioned is of other character. Three theories suggest them- 

 selves as capable of accounting for the phenomena : first, that there is 

 in the pons or higher up a center which inhibits chemical movements in 

 the body, and that the section of the cord at the pons takes off from 

 the general tissues this restraining influence ; second, that the animal 

 heat is mainly made in the muscle, and that the vasomotor center of 

 the muscles is situated above the medulla, so that it is paralyzed when 

 the section is made between the pons and medulla ; third, that the sec- 

 tion irritates the vasomotor centers and thus inflaences heat i^roductiou 

 by influencing the circulation. 



The irritation theory was disproved by direct experiment, careful 

 cardiometrical studies showing that the arterial pressure is not seri- 

 ously affected by the oijeration, and that the circulation after the opera- 

 tion preserved all its normal relations with the organism below the sec- 

 tion. Again, the persistence of the increased heat production for 

 twenty-four hours seems very inconsistent with the irritation theory. 

 Any one who has divided a spinal cord knows that all symptoms of irri- 

 tation subside usually in a few minutes after a clean section. Finally, 

 in two experiments punctures were made into the region of the junction 

 of the medulla and pons, just sufficient to cause irritation, and the result 

 was lessening of the heat production. 



The conclusion that there is among the upper nerve-centers one which 

 directly or indirectly controls the production of animal heat independ- 

 ently of the vasomotor centers of the medulla was further corroborated 

 by a series of experiments of a different character from any as yet 

 spoken of. If a sensitive nerve be galvanized there is a fall of the bod- 

 ily temperature, which has usually been attributed to changes in the 

 cirdblation and respiration. By experiments, which will be reported 

 fully in the memoir, this fall of temperature is shown to be independent 

 of the respiration, or of any changes in the blood pressure, such as is 

 produced through the governing vasomotor centers of the medulla. Fur- 

 ther, when the pons is separated from the medulla by section, it is impos- 

 sible to produce a decided fall of the bodil,\' temperature by galvanization 

 of a sensitive nerve, although both circulation and respiration are appar- 

 ently attected as in the normal animal. The only plausible explanation 

 of this is that there is a nerve center above the point of section, which 



