ANIMAL HEAT 



449 



The second part of the calorimeter consists of a closed system of tubes 

 and absorption vessels through which the air is kept moving under the action 

 of a blower and thus kept in a respirable condition. As the air leaves the 

 chamber it passes through two absorption vessels by which the water and 

 carbon dioxid are successively absorbed and collected by sulphuric acid and 

 soda lime respectively. The air then passes through an additional sul- 

 phuric-acid vessel which absorbs any water carried from the soda-lime vessel 

 by the air and so back into the chamber. By weighing these absorbing 

 vessels before and after the experiment the amount of water and carbon 

 dioxid are readily determined. The oxygen of the air of the chamber that 

 is utilized for respiration purposes is restored by the admission of oxygen 

 from a cylinder in necessary amounts by special automatic devices. The 

 amount of oxygen entering the chamber is determined by weighing the 

 cylinder before and after the experiment. The loss in weight shows the 

 oxygen consumed. Of course, the air of the chamber must be analyzed 

 to correct certain errors that may possibly arise. 



With the calorimeters described in the foregoing paragraphs it is pos- 

 sible not only to determine directly, but also indirectly, from the amounts 

 of protein, fat, and carbohydrate metabolized (calculated from the C,H,O, 

 and N eliminated and O absorbed) the heat produced and dissipated each 

 day under a great variety of conditions e.g., when the subject is fasting or 

 living on the customary diet; when resting or doing a fair days work; when 

 in health or in disease, etc. 



i. During Fasting. In an experiment extending over a fasting period 

 of seven days' duration, recorded at length by Benedict, the heat was 

 determined directly, and also indirectly, from the materials metabolized. 

 Some of the results of this experiment are shown in the following tables: 



METABOLISM OF S. A. B. DURING A SEVEN-DAY FAST 



Many similar experiments have been made by Benedict and by others with 

 different forms of apparatus. As an average result it may be stated that 

 in the fasting condition and doing light work there is an average heat-dissipa- 

 tion of 31 or 32 calories for each kilogram of body-weight, thus making a 

 total for a man weighing 70 kilograms of 2170 or 2240 Calories. 



2. On the Customary Diet. When an individual is supplied with the food 

 materials composing a customary diet, and is therefore in the physiological 

 condition, the amount of heat produced and liberated is necessarily in- 

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