COMPOSITION OF ANIMALS AND OF FEEDING STUFFS 71 



If a different solvent is used, this should be specified in the state- 

 ment of the analysis. 



109. Crude fiber. The so-called crude fiber of feeding stuffs 

 is determined by boiling them first with dilute acid and then 

 with dilute alkali under strictly defined conditions of concen- 

 tration and time, and washing the undissolved residue with 

 alcohol and ether. The residue, after deducting the small 

 amount of ash remaining in it, constitutes the crude fiber. 



Crude fiber as thus obtained contains most of the cellulose, 

 lignin and cutin of the feeding stuff, along with more or less 

 of the more difficultly soluble hemicelluloses, particularly those 

 containing pentosans. The proportion of pentosans contained 

 in the crude fiber naturally varies according to the nature of 

 the feeding stuff. Tollens, l for example, obtained the fol- 

 lowing figures for the crude fiber of meadow hay and of brewers' 

 grains : 



110. Nitrogen-free extract. All the ingredients of feeding 

 stuffs which are not included in the foregoing six categories, 

 viz., water, ash, protein, non-protein, ether extract and crude 

 fiber, are usually grouped together under the collective name of 

 nitrogen-free extract. The significance of the name is evident. 

 By definition the nitrogen-free extract includes all those non- 

 nitrogenous organic constituents, other than fat, which are 

 extracted from the feeding stuff in the process of determining 

 the crude fiber. The amount of nitrogen-free extract in a 

 feeding stuff is not ascertained by any process of direct deter- 

 mination but simply by subtracting the sum of the other six 

 groups from 100 per cent. Such a residual group naturally in- 

 cludes a great variety of substances of very diverse nature, 2 



1 Jour. Landw., 45 (1897), 103. 



2 For an enumeration of the principal ingredients of the nitrogen-free extract, 

 compare Tollens, Jour. Landw., 45 (1897), 295. 



