Digestion Experiments With Wethers. n 



The water in a powdered and air dried material is determined 

 by heating at the temperature of boiling water for several 

 hours in an atmosphere of hydrogen. If the heating in the 

 process of drying was carried on in -the air instead of in hy- 

 drogen, some of the material might possibly be oxidized, giv- 

 ing an incorrect result for the amount of water. 



ASH. When plants are burned completely, a portion is 

 left as an ash. It contains the mineral ingredients which are 

 necessary to the animal, such as lime, phosphates, potash, soda, 

 etc. These form an important part of many of the tissues, 

 especially the bones, the mineral portion of which is largely 

 calcium phosphates. With ash is also included the inorganic 

 matter clinging to the immediate surface of the plants. This 

 is considerable where the plant is covered with fine hairs or is 

 sticky. The mineral constituents are not all digested, so a part 

 is always found in the feces. 



ETHER EXTRACT. Many chemists designate this as crude 

 fat. It contains besides the fat some of the coloring matter, 

 gums, etc., which are soluble in absolute ether. Roughly, it 

 represents the amount of fat. It is determined by passing 

 ether through the material for several hours. The ether ex- 

 tract is considered to have a value of 2.4 times the carbo- 

 hydrates. Fat is used principally as a fuel to furnish heat to 

 the animal body. When not needed as such, it is stored up 

 in the body. 



CRUDE: FIBER. This is the woody portion of the plant 

 found principally in the cell walls. It was once thought to be 

 indigestible, but is now known to be partially digested and 

 has a nutritive value similar to the starches and sugars. It is 

 determined by dissolving out all other constituents of the food 

 with dilute acids and alkalies, drying, weighing, and burning. 

 The residue, being insoluble ash, is subtracted from the pre- 

 ceding weight to obtain the amount of fiber. 



