Compound Celluloses 165 



are the results of an experiment carried out under the usual 

 conditions. 



Undissolved by treatment . . 40*3 p.ct 



Soluble and reprecipitated by acids . . 32-4 ,, 



,, and not reprecipitated by acids . 27-3 ,, 



The straws and products of this class have thus been 

 investigated in various directions, but by no means exhaus- 

 tively. A systematic investigation on the lines of research 

 herein indicated would be a valuable contribution to our 

 knowledge. 



' Crude Fibre.' ' Rohfaser.' In connection with the ligno- 

 celluloses of cereals, the opportunity arises to discuss an artificial 

 product with which agricultural chemists are familiar under the 

 above description. In arriving at the nutritive value of food-stuffs 

 it is necessary to discriminate between digestible and indigestible 

 constituents. It has long been known that to the former belong 

 chiefly the proteids, the water-soluble carbohydrates and fats ; and 

 to the latter, in general terms, the cellular tissue of vegetable 

 food-stuffs. Between these two extreme groups lies the aggregate 

 of compounds known as * non-nitrogenous extractive matters.' It 

 will be evident from discussions in this treatise (p. 86) that this 

 complex admits of being resolved, by various processes of hydrolysis 

 and oxidation, into carbohydrates of known constitution, or deriva- 

 tive products which determine the constitution of the groups from 

 which they are formed. This aggregate is dissolved by treatment 

 with weak hydrolytic agents, acid and alkaline, and the residue is 

 the complex in question, known as crude fibre. A standard process 

 for estimating this complex, which has been largely, in fact gene- 

 rally, used by agricultural chemists, is that known as the * Weende 

 method.' This consists in boiling the material to be analysed with 

 dilute sulphuric acid (1-25 p.ct. H 2 SO 4 ), and afterwards with 

 dilute alkaline solution (1*25 p.ct. KOH), washing, drying, and 

 weighing the residue. As the process of animal digestion may be 

 briefly defined as an exhaustive series of hydrolyses under alter- 

 nately acid and alkaline conditions, the method in question cer- 

 tainly gives a crude measure of the proportion of the material 

 resisting the natural process of digestion. On the other hand, as 



