EVOLUTION OF IIEAT. 529 



of all .similar phenomena in "cold-blooded" animals, which have compara- 

 tively but feeble power of maintaining an independent temperature, exhibit 

 no such uniformity; yet even in the lowest Vertebrata, according to Mr. 

 Gulliver, 1 the temperature of the body is from 2 3 to 5 warmer than that 

 of the medium in which they live. Heat, which is a mode of motion, is 

 generated whenever stronger chemical affinities than those which were pre- 

 viously iu action, are satisfied ; hence the temperature rises in muscles that 

 are made to contract, and in glands when they are iu the active perform- 

 ance of their function. The liver, spleen, kidneys, and glands of the intes- 

 tinal tube, 2 with the brain, 3 the muscles during exercise, and the blood 4 

 itself are the chief generators of heat in the body, because iu all these parts 

 active processes of oxidation are taking place by which the constituents 

 of these organs and tissues are reduced to lower and more stable planes 

 of composition and a certain amount of force is set free in the form of heat. 

 We shall now inquire, in the first place, into the amount of heat thus gen- 

 erated by Man ; and then into the sources of its production. 



4l>5. Our present knowledge of the ordinary Temperature of the Human 

 Body under different circumstances, is due to the investigations of a multi- 

 tude of observers, references to many of which will be found in Wunderlich's 

 exhaustive treatise. A series of observations made by Dr. J. Davy 5 included 

 114 individuals of both sexes, of different ages, and among various races 

 and different latitudes, and under various temperatures; the external tem- 

 perature, however, was in no instance very low, and the variations were by 

 no means extreme. The mean of the ages of all the individuals was 27 

 years. The following is a general statement of the results, the temperature 

 of the body having been ascertained by a thermometer placed under the 

 tongue : 



Temperature of the air, . . 60 I Average temperature of the body, . 08.28 

 " " . . 69 " " " . 98 15 



" " 78 " " " 98 80 



" " . . 80 



" " . . 82 



Mean of all the experiments, . 74 



Highest temperature of air, . 82 



Lowest temperature of air, . 60 



5 " " . 99.21 



,0 



o 



" . 99.67 



" 99 9 



Mean of all the experiments, . . 100 

 Highest temperature of body, . . 102 

 Lowest temperature of body, . . 96. 5' 



From this we see that the variations noted by Dr. Davy, which were evi- 

 dently in part the consequence of variations in external temperature, but 

 which were also partly attributable to individual peculiarities, amounted to 

 5|- degrees; the lower extreme might be found to undergo still further de- 

 pression, if the inquiries were carried on in very cold climates. Wunderlich 6 

 gives as the result of the numerous observations made by himself and others 

 of late years, a lower mean temperature than Dr. Davy, and states that the 



1 Lecture IX, Med. Times and Gaz , Jan. 17th, 18(53. 



2 See Winternitz, in Strieker's Med. Jahrbiicher, 1871, p. 180. 



3 Ek'id.'nhain, Pfiiiger's Arohiv, Bd. iii, p. 504. Funkc, Physiologic, 1873, p. 306. 



4 See Gamgee, On Heat Generated in the Blood during Arterialization, Brit. 

 Assoc. Keporfs, 1871. 



5 See Anatomical and Physiological Researches. Wiin'lerlieh's treatise has been 

 translated by Dr. Woodman for the New Syd. Society. See also Brown-Sequard 

 (Journal de la Physiologic, 18-39, p 549), whoso experiments essentially corroborate 

 those of Dr Davy, as well as the older ones of MM. Eydoux and Souleyet (Comptes 

 Rendus, 1838, p. 457), except that he found a greater difference in the temperature 

 of the men he examined, though the variation of the atmospberic temperature was 

 much less. 



6 Loc. cit., p 82. 



