Ml TAB0U8M 



with accuracj in both intake and output. Prom balai 

 and output of carbon and nitrogen and from information obtain ob- 



serving the ratio between the amounts of oxygen consumed by the animal 

 and of carbonic acid excreted, we can draw Ear-reaching conclusi* 

 garding the relative amounts of protein, fa1 and carbohydrate that 1 

 been involved in the metabolism. 



As has already been stated, thi ntial nature of the metabolic pn 



< 38 iii animals is one of oxidation thai is, one by which large unstable 

 molecules are broken down to those thai are simple and stable. Dur- 

 ing this process of catabolism, as it is called, the potential e 



away in the Large molecules l omes liberated as actual or kinetic energy 



thai is, as movemenl and heat. It therefore becomes of imports 

 compare the actual energy which an animal expends in a given timo with 



the energy which has meanwhile 1 □ rendered available bj metabolism. 



W'c shall first of iill consider this Bo-called energy balanci and then ■ 

 i to examine somewhal more in detail the material balance of the body. 



ENERGY BALANCE 



The unit of energy is the large calorie I written C.)j which is the amount 

 of heal required 1" raise the temperature of one kilogram of water through 

 one degree (Centigrade) of temperature. We can determine the cal< 

 value by allowing a measured quantity of a substance to burn in c 

 pressed oxygen in a steel bomb placed in a known volume of water at a 

 certain temperature. Whenever combustion is completed, we find out 

 through how many degrees the temperature of the water has bea 

 raised and multiply tins by the volume of water in liters. Measured 



in such a calorimeter, as this apparatus is called, it has 1 a found that 



the number of calories Liberated by burning one gram of each of the proxi- 

 mate principles of t 1 is as follow - : 



Carbohydral ~ rch |J 







Protein 







The same llUtnlier of Calories will he lilierated at whatever lad 1 the com- 



bustion proceeds, provided it results in the same end products, When 

 a substance, such as sugar or fat, is burned in the pri s i, it 



yields carbon dioxide an. I water, which are also the end produ the 



metabolism of these foodstuffs in the animal bodj ; therefore, when a gram 

 of sugar <>r fat is quickly burned in a calorimeter, it rele - - the same 



■ p •■ 



formi 



