974 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Although leguminous foods contain an abundance of nitrogen, it must 

 be remembered that it is not all available unless a moderate quantity only 

 enter the diet. 



The potato may be taken as the best representative of a carbonaceous 

 food. Comparing it with rice, one of the least nutritious of the cereals, 

 the analyses are as follows : 





Potato. 



Rice. 



Water 



75*0 



14-6 



Albuminoids. 



. 1-2 



7-5 



Extractives (solanine, &c.) 



. 1-5 





Starch 



. 18-0 



76-0 



Dextrine and pectose 



. 2-0 





Fat 



. 0-3 



0-5 



Cellulose . 



. 1-0 



0-9 



Ash 



. 1-0 



0-5 





Nutrient Ratio. 



Nutrient 



Potato 



1 : 17 



22 



Rice . 



1 : 10 



84 



Flesh-forming albuminoids in the potato being practically nil, the two 

 useful ingredients are the starch and the ash. It will be seen how poor 

 rice is also in nitrogen, though exceptionally rich in starch. Hence its 

 use is like semolina, or even tapioca, for the making of puddings. 



With reference to salts contained in the mineral matter or ash of 

 plants, it has already been pointed out that they are diffused in growing 

 vegetables, but especially located in seeds. Herein, as observed, lies the 

 importance of retaining the outermost parts (excepting the superficial 

 layer) of grains of cereals, which are rich in phosphate of lime, magnesia, 

 etc. Potash also abounds in ordinary land plants, while table-salt occurs 

 in saline and maritime plants ; but as these latter do not form any part 

 of ordinary diets, this salt has to be supplied in addition. One use of 

 salads, besides being a refreshing cool diet, lies in the salts they contain ; 

 for, although having no amount of nutrition to speak of, in the proper 

 sense of the term, salts are retained in them, while to a considerable ex- 

 tent they are removed by cooking. Their function in the human body, as 

 also in the plants themselves, is for the transference, absorption, and 

 elaboration of oxidisable nutrients. Watercress, it may be mentioned, is 

 particularly rich in salts. 



The value of foods in supplying force or energy has had more atten- 

 tion paid to it of late years, since the exact value of work capable of being 

 executed can be ascertained from the amount of heat given by the burn- 

 ing of any organic substance. Oxidation is, in fact, the measure of work. 



The non-nitrogenous compounds have been called "heat-givers"; a 

 better term is perhaps " force-suppliers." Of these, starch and sugar, 

 taken as types of their polymers, are called carbohydrates, because the 

 hydrogen and oxygen enter their composition in the proportion which 

 forms water ; while oil has a less amount of oxygen, so that its carbon 

 and hydrogen require more oxygen to be burnt. It is thus the greatest 

 force-producer of any organic substance.* 



* The staple diet of a Suffolk labourer is bread, cheese, and fat bacon. 



