NUTRITIVE VALUE OF FEEDING STUFFS 45 
the feeding stuff, and may be used by animals for maintenance and 
production. 
Various units have been employed for measuring the heat of 
combustion. The common unit is a Calorie, which represents the 
amount of heat required to raise the temperature of one kilo- 
gram of water one degree Centigrade, or that of a pound of water 
very nearly four degrees Fahrenheit. A therm, as proposed by 
Armsby, means 1000 Calories, the amount of heat required to raise 
the temperature of 1000 kilograms of water (or 2204.6 pounds) 
one degree Centigrade. _This unit has been quite generally adopted 
of late and will be used in the following pages. 
The various components of feeding stuffs contain certain 
amounts of oxygen and are, therefore, partially oxidized. Carbo- 
hydrates thus contain about 50 per cent of oxygen, fats 10 to 12 per 
cent, protein 22 per cent (pp. 9, 12, 14). The amount of heat evolved 
in the combustion of any organic material depends on the propor- 
tion of oxygen it requires for complete oxidation of the carbon, 
hydrogen, nitrogen, and other chemical elements contained therein. 
This amount can be calculated in the case of stbstances of known 
composition, and directly determined in a so-called calorimeter. 
The Calorimeter.—This apparatus consists of a well-insulated, 
double-walled compartment, into which a platinum shell or bomb 
is introduced and submerged in water. A weighed small amount 
of the substance whose heat of combustion is to be determined is 
introduced into this shell with compressed oxygen, and ignited 
by means of an electric spark. By noting the rise in temperature 
in the’surrounding water the amount of heat given off by the sub- 
stance on complete combustion can be calculated. 
Chemical Energy.—It has been found by direct experiments 
that the chemical energy of different classes of nutrients and feed- 
ing stuffs is as follows: 
Chemical Energy in 100 Pounds, in Therms 
Pure nutrients 
Protein: Carbohydrates: 
Wheat gluten ........... 272 Starch, cellulose ......... 190 
Gliadin, serum albumen... 268 Glucose ..... 02. c cee enees 170 
Egg albumen, pure lean Sucrose, lactose, maltose.. 179 
MEAE: sipacisiede eee ee 259 ~=Fats: 
Blood fibrin ............ 256 Steers and swine ....... 425 
Sheep ss0) cseaiessars cies 427 
Corn Oi] ........ eee eee 421 
; Common feeding stuffs 
Flaxseed meal .......... 267 Alfalfa hay, mixed hay and 
Linseed oil meal......... 194 oat straw .........06. 173 
Corn meal ............0% 171 Rice meal ...........0005 170 
