- 10 Composition and Nutritive Value of Strain. 



that the same description of food which is assimilated in a great 

 measure by one kind of animal often remains to a much greater 

 extent undigested when given to another. Thus it has been 

 proved by direct experiments that cows can extract a great deal 

 more nourishment from straw-chaff than horses, and that sheep do 

 not appear to digest chaff so readily as cattle. 



Although chemical analysis cannot decide with anything like 

 precision the most interesting and practically important point on 

 which the whole controversy of the feeding value of straw hinges, 

 we must not suppose that it is altogether useless to submit to 

 analysis the various kinds of straw used on the farm. I hope to 

 be able to show that the investigation undertaken by me at the 

 request of the Chemical Committee of the Royal Agricultural 

 Society has brought to light several matters of considerable 

 practical importance, and is suggestive of others of interest. 

 The following points, at all events, can be readily ascertained. 

 In the first place, we can determine with precision the amount 

 of oil, certainly the most valuable constituent of straw ; secondly, 

 the proportion of albuminous or flesh-forming matters ; and thirdly, 

 the amount of organic substances soluble in'water, such as sugar, 

 mucilage, gum, extractive matters, &c. The mineral portion or 

 ash, of course, is easily ascertained by burning a known quantity 

 of straw in a platinum capsule, and weighing the ash which 

 remains behind. 



The proportion of oil is easily obtained by exhausting a 

 weighed quantity of straw in an appropriate apparatus with 

 ether, and evaporating the ethereal solution of oil to dryness. 

 Albuminous compounds are now usually determined in the 

 indirect manner by combustion with soda-lime, and multiplica- 

 tion of the percentage of nitrogen by 6J. A weighed quantity, 

 exhausted with cold and afterwards with boiling water, produces 

 the proportion of soluble matter, consisting of sugar, mucilage, 

 extractive matter, and soluble saline matters. If the portion of 

 straw previously exhausted with ether and water is subse- 

 quently boiled with a solution containing 1 per cent, of caustic 

 potash, the insoluble albuminous compounds are dissolved ; 

 and by treating the residue left after boiling with potash-solution, 

 with dilute sulphuric acid, and finally washing again with water, 

 we obtain the amount of cellular and woody fibre in the straw. 



It has been stated already that this process does not furnish 

 corresponding results in two or three separate determinations. 

 Nevertheless it is desirable in detailed analyses to have recourse 

 to this process, which at least allows us to form some idea of the 

 readiness with which the part of straw which is insoluble in 

 water, and which may be termed crude woody fibre, is attacked 

 by dilute alkalies and acids. There can be no doubt that the 



