ANIMAL HEAT. 261 



temperature of the animal, and the loss from the apparatus by external 

 cooling. By this method it was found, as the average result of five 

 observations, that a dog of 5.392 kilogrammes' weight, at rest and in 

 the fasting condition, produced in one hour 12.63 heat units; that is,. 

 2.34 heat units for every kilogramme of bodily weight. According 

 to these experiments, the heat-producing power in the dog and that 

 in man are nearly the same ; that of the dog being rather the more 

 active of the two. 



Normal Variation of Temperature in the Living Body. The tem- 

 perature of the body is not the same throughout, but increases, for a 

 certain distance, from the exterior toward the central parts. Like any 

 other substance of higher temperature than the air, the animal body 

 is constantly losing heat from its surface ; so that the integument and 

 the parts immediately subjacent, which are more exposed to this cool- 

 ing influence than the internal organs, have a temperature slightly 

 below that of the body in general. Accordingly, whenever the external 

 air rises to the neighborhood of 37 or 37.5 C., it feels uncomfort- 

 ably warm; because, although this is the normal temperature of the 

 internal organs, it is considerably above that of the skin, which is 

 readily sensitive to variations of cold or warmth. The cooling influ- 

 ence of the atmosphere is, however, moderated by the circulatory move- 

 ment of the blood ; since the warmer blood coming from the internal 

 parts supplies the integument with fresh quantities of heat, and thus 

 tends to compensate for its external loss. 



But notwithstanding this compensation, the difference in temperature 

 between the external and internal parts of the body is alwa per- 

 ceptible during health. If the bulb of a thermometer be held for .ome 

 minutes between the folds of skin in the palm of the hand, it will 

 stand at 36.4 ; in the axilla, at 36,6 ; under the tongue, it will reach 

 37.2 ; in the rectum, 37.5 ; and Dr. Beaumont found, in the case of 

 Alexis St. Martin, that the thermometer, introduced into the stomach 

 through the gastric fistula, often indicated a temperature of 37.8. It 

 is evident that, in order to ascertain the internal temperature of the 

 body, the bulb of the thermometer should be inserted so deeply as to 

 pass beyond the superficial zone affected by the process of external 

 cooling. Even when beneath the tongue it is in contact with parts 

 which are slightly cooled by the passage of the air in respiration, 

 and accordingly does not reach the maximum temperature of the body. 

 For this, it must be so deeply inserted into the abdominal cavity or the 

 rectum, that a further introduction produces no increase in the indicated 

 temperature. This is the method usually adopted in physiological 

 observations. 



Beside the difference from the above cause between the surface and 

 the interior, the internal temperature also varies within narrow limits, 

 according to different physiological conditions. Jurgensen * has shown 



* Die Korperwarme des gesunden Menschen. Leipzig, 1873. 



