QfyG EXPERIMENT STATION RECORD. 



tben either evaporating to dryness an aliquot of the aqueous extract, 

 weighing, and cal(*ulating to tlie original substance; or drying the resi- 

 due from the extraction and determining the substance dissolved by 

 difference. Henneberg and Stohmanu boiled 4 to 5 gm. of the finely 

 ground substance one-half hour with 800 cc. of water, then digested 

 to 8 hours in a water bath, made the volume to 1 liter on cooling, fil- 

 tered, evaporated 500 cc. of the filtrate to dryness, weighed the residue, 

 and calculated it to the original substance. 



In this aqueous extract the reducing and nonreducing sugars can be 

 determined by Fehling's solution, and the dextrin, starch, etc., after 

 separating with alcohol, etc.^ 



Other methods. — (Irandeau and Leclerc- tried other methods of extrac- 

 tion for determining the digestible nitrogen-free extract of meadow 

 hay and oats. Thej^ digested the substances first with 95 per cent 

 alcohol and determined the glucose, tlien with diastase to separate the 

 starch, which was inverted with sulphuric acid and determined as 

 dextrose; and finally with 2 per cent sulphuric acid, which dissolved a 

 portion of the cellulose. 



By this method of extraction, the principal carbohydrates of impor- 

 tance in nutrition aredissolved, but not the less soluble substances which 

 are brought into solution by the action of the digestive fluids of the 

 body. The method also contains other doubtful factors. 



None of these methods for determining the digestible nitrogen-free 

 extract have come into general use. The determination of the aqueous 

 extract is not only more convenient but also better adapted to furnish 

 an indication of the approximate amount of digestible nitrogen-free 

 extract. Ilenneberg's aqueous extract method shows approximately 

 the nitrogen -free extract digested by the stomach of an animal within 

 12 to 24 hours. 



Digest ihility of crude fiber. — As is well kiiown, from 2 to 3 days or 

 even a longer time may elapse before the undigested portion of the food 

 is entirely excreted from the body, and during this time processes take 

 place which can not be imitated by the solvents employed in the 

 Weende method. 



Digestion experiments with animals have shown that the crude fiber 

 is by no means unattacked in the digestive tract, but is more or less 

 dissolved, and so is not completely recovered in the excreta. During 

 the long x)eriod of digestion within the body the crude fiber under- 

 goes a special fermentation, due to the action of bacteria. As a result 

 a part of the crude fiber, especially of the cellulose, is dissolved with 

 the formation of lactic acid, carbon dioxid, marsh gas, etc. A part of 

 the crude fiber is digested, and consequently less crude fiber is found 

 in the dung than was consumed in the food.-^ 



' See Kihiig, Untersuchuug landw. und ueweblicb wicbtiufer Stoffe. I'.erliii, 1891, 

 p. 224. 



2 Ann. Sci. Agrou., 1886, II, p. 357. 



^Investigntious of Elleuberger and Ilofnieistev, "\Vc,isk<>, Tai)poiiier, 1". Holdclieiss, 

 and others. 



