DIETARIES AND RATIONS. 



these ingredients it is necessary that a small but adequate amount 

 of phosphoric acid and of potash should be present, while common 

 salt is, of course, invariably added. No special provision for the 

 supply of the other mineral or ash-constituents of human food 

 need generally be made, as the lime, magnesia, iron, and sulphuric 

 acid (or sulphur) required are furnished in abundance by most 

 varieties of food, such, for instance, as wheat, buckwheat, and the 

 millets. With rice, however, the case is different. This grain 

 contains very little mineral matter, yielding on complete burning 

 only about half a grain of ash for each hundred grains of cleaned 

 rice taken for the purpose of the experiment. Fortunately, fresh 

 fruits, green vegetables, and especially the different kinds of pulse, 

 which are frequently used to supplement the other deficiencies of 

 rice, supplement also its deficiency in mineral matter. Thus i ounce 

 of pigeon-peas (Cajanus indicus) contains as much phosphoric acid 

 and nearly twice as much potash as 3^ ounces of rice. So likewise, 

 in adding pulse to rice in order to furnish the due proportion of 

 albuminoids or " flesh-formers," we introduce also sufficient supplies 

 of lime, magnesia, etc. 



We may then leave out of consideration the mineral matter 

 and the common salt, and confine our attention to the three main 

 constituents of food, namely, the albuminoids, the oil, and the 

 starch. Reference should be made to pp. 2,4, 6, and 7 for explanations 

 of the meanings attached to these three terms, especially as to the 

 inclusion, under the name "starch," of sugar, dextrin, pectose, 

 and other allied compounds, and also as to the expression " starch- 

 equivalent of fat or oil;" this we assume to be 2*3, so that we 

 may convert (for purposes of calculation) the oil of a ration into its 

 starch-equivalent by multiplying it by this coefficient. 



Although the various causes which combine to render a mixed 

 diet not only desirable but necessary, if robust health is to be 

 maintained, have been already described, it will serve to give 

 special significance to the general argument on this point if we 

 illustrate it here by a few selected examples. Scarcely any single 

 article of food (and we confine ourselves in this Handbook to the 

 food-staples of the vegetable kingdom) is complete and properly 



