4 VOELCKER on the Chemistry of Food. 



gical or other strictly scientific literature. Having had frequently 

 occasion to observe the difficulty under which the practical man 

 labours in finding that information which he is anxious to obtain 

 with respect to the composition and practical value of food, it 

 has appeared to me desirable to facilitate in some measure his 

 search for information on this subject. To this end I have 

 collected the most trustworthy analyses, and I hope, after rejecting 

 all those which bear upon them the impress of imperfection or 

 impracticability, to present to you in a systematic order a suffi- 

 ciently correct account of our existing knowledge of the com- 

 position and practical feeding value of the more important feeding- 

 stuffs employed by the farmer for maintaining the animals on a 

 farm, or for rearing and fattening of stock. With a view of 

 lessening much that is necessarily tedious in such an account, I 

 shall endeavour to intersperse it with some general practical 

 remarks which the various headings will suggest, and shall con- 

 clude by pointing out a few considerations which ought to be 

 well weighed in estimating the economical value of feeding- 

 materials. Before entering into details, however, it will be 

 necessary for me briefly to allude to the principal divisions of the 

 constituents of food, and to their respective adaptation to the 

 wants of the living animal. 



If we expose to a strong heat in an open vessel wheat, oats, 

 or barley, turnips and mangolds, clover, artificial or natural 

 grasses, and indeed all kinds of food raised for the use of man 

 or animals, they are dissipated for the greater part, and but a 

 small quantity of a generally white ash is left behind. The 

 incombustible portion, or ash, amounting rarely to more than 6 

 per cent, of the whole mass of the dry substance, consists prin- 

 cipally of two classes of substances: namely, first of earthy 

 matters, insoluble in water ; secondly, of saline and soluble sub- 

 stances. The earthy insoluble matters, in the majority of cases, 

 consist chiefly of a combination of phosphoric acid with lime, 

 which, constituting two-thirds of the bones of animals, is called 

 bone-earth. The earthy portion of the ash supplies the animal 

 with the materials for the formation of its bony skeleton. The 

 saline constituents of the ash of food consist chiefly of common 

 salt and of phosphate of soda, which two combinations enter 

 largely into the composition of blood, and likewise of salts of 

 potash which abound in the juice of flesh. The saline matters 

 thus supply the blood, juice of flesh, and various animal juices, 

 with the necessary mineral constituents. The organic or com- 

 bustible part of all food is composed of a great variety of organic 

 compounds, such as starch, gum, sugar, cellular fibre, albumen, 

 casein, gluten, c. But all these compounds may be grouped 



