Body-Temperature. 117 



perspiration is not a measure of either the carbon dioxide or the water-vapor 

 given off from the body, but includes certain amounts of carbon and hydrogen 

 from organic material. 



The water leaving the body in the form of vapor may in large part result 

 from the simple evaporation of water from the lungs and skin. A small quan- 

 tity, however, is water resulting from the oxidation of organic hydrogen, and 

 since in the oxidation of every gram of such hydrogen there are 8 grams of 

 oxygen taken from the air, obviously the 9 grams of water-vapor thus formed 

 from organic hydrogen does not represent a loss of weight to the body of more 

 than 1 gram of hydrogen. Under conditions of rest there are from 200 to 300 

 grams of water resulting from the oxidation of organic substances leaving the 

 body each day, and one-ninth of this amount, or approximately 30 grams, is 

 the weight of the organic hydrogen which is lost from the body. It is thus 

 seen that with an hourly insensible perspiration of about 40 grams, the de- 

 crease in body-weight in 24 hours due to the loss of organic hydrogen would 

 be nearly equal to the insensible loss for 1 hour. 



A considerable proportion (eight-elevenths) of the carbon dioxide exhaled 

 is oxygen, which is derived from the air, and inasmuch as in ordinary rest 

 experiments there are about 700 grams of carbon dioxide per day, it can be 

 seen that the carbon dioxide for 24 hours represents only about 190 grams of 

 carbon lost from the material of the body, the remainder being due to oxygen 

 from the air. On the other hand, the total weight of water vaporized from 

 the lungs and skin, with the single exception of the oxygen in the water formed 

 by the oxidation of organic hydrogen, is lost from the body, and is a true in- 

 sensible loss. 



The insensible loss is, then, only a rough approximation of the total loss of 

 water-vapor from the body, and if a more correct determination is desired, one 

 must deduct in rest experiments about 190 grams of carbon and about 30 

 grams of organic hydrogen lost from the material of the body in the course of 

 24 hours. 



Body-Temperature. 



It has long been known that the temperature of the human body remains 

 relatively constant. The old " blood-heat " of the earlier investigators was 

 supposed to be a constant, and this was, indeed, one of the earlier fixed points 

 in thermometry. With the development of more exact thermometers it was 

 seen that, strictly speaking, this is not true, and that the body- temperature 

 varies considerably both with regard to the portion of the body in which the 

 temperature is taken and with regard to the influence of factors, such as mus- 

 cular exercise, and particularly with regard to disturbances of metabolism ac- 

 companied by fever. 1 It is not possible here to go into a consideration of the 



1 For a most ingenious method of studying body temperatures see Gamgee, Philo- 

 sophical Transactions, 1908, 200, p. 219. 



