THE NITROGEN-FREE EXTRACT OF FEEDING STUFFS. 



655 



The ash was determined iii the residue from one sample by incinera- 

 tion and the protein in the other by the Kjeklahl method. The ash 

 and protein deducted from the residue gave the crude fiber and undis- 

 solved nitrogen-free extract; and this plus tlie protein, fat, and ash 

 found in the orig-inal substances, deducted from the amount taken, 

 showed the nitroiien-frec extract digested. 



Tliis method while not so tedious as a feeding experiment is quite 

 long and complicated. It would j»robably be employed if it always gave 

 correct results, but its accuracy has been questioned by Pfeiffer' who 

 found a large ditference between the results as obtained by Stutzer and 

 Isbert and those obtained in natural digestion trials on animals. 



Water-soluble 2)ortion of nitrogen-free extract. — Percentaf/e of aqueous 

 extract. — Otlier chemists have undertaken to determine by the direct 

 method the amount of carbohydrates and similar substances in feeding 

 stuffs, and how nuich of this is digestible. 



nenneberg and Stohraann ' found, for example, that in common feed- 

 ing stuffs (oat straw, wheat straw, bean straw, clover, and meadow hay) 

 the amount of substance soluble in water was approximately equal to 

 the digestible portion of the nitrogen-free extract. 



Thus the following results were obtained: 



Jltlalion between digestible u it ro(j en-free extract and aqueous extract. 



In other cases the agreement was even better. Kiihn, Aronstein, 

 and H. Schulze ' conflrmed this deduction, and J. Konig^ approximately 5 

 and, although Maerckerand E. Schulze'' obtained less concordant results, 

 the api)roximate agreement of the acjueous extract of feeding stuffs 

 with the digestible nitrogen free extract is at least very noteworthy. 



Since the determination of water soluble substances — that is, the per- 

 centage of aqueous extract — is comparatively very simple and rapid, it 

 is of very great practical value for the judging of feeding stuffs. It is 

 best carried out by repeatedly extracting the material with water, and 



'Centbl. agr. Chem., 17 (1888), p. 115. 



^Weendcr Beitriigo, vol. 2, p. 253; Neue Weender Reitriige, p. 344. 

 =' Jour. I.andw., sor. 2, 2 ( 1867), p. 33. 



''Dietrich and K(>uig, Dio Zusanimensctziiug und Verdaulichkeit der I'^itteriiiittul, 

 part 2, p. 1163. 

 6 Jour. Landw., ser. 2,6 (1871), p. 67. 



