DIETETIC VALUES OF FOOD-STUFFS PREPARED BY PLANTS. 969 



table-salt, is the only one wanting in ordinary vegetables, so it has, of 

 course, to be supplied as an extra adjunct to a diet. 



The natural orders or families of plants which furnish food to man 

 are not very numerous ; one or two contain a large number, while isolated 

 plants in others have special values of their own respectively. The chief 

 is Graminece, or grasses, of which the cultivated members or cereals are 

 the most important of all foods. The grains are remarkable for contain- 

 ing considerable quantities of both nitrogenous and non-nitrogenous food- 

 stuffs, as well as mineral matters, or " ash." Indeed, cereals alone supply 

 the greater part of all the materials required for restoration and the 

 supply of energy. The Legummosce follow suit; but their percentage 

 of albuminoids is excessively high in comparison with that of cereals and 

 other foods, so that they require to be supplemented by more farinaceous 

 (starch) and oleaginous substances to form a complete diet. Of isolated 

 species, the potato, sweet potato, and yam are examples of vegetables of 

 wide-spread cultivation, resembling each other in being poor in albu- 

 minoids, but rich in starch. Hence they form excellent adjuncts to meat 

 and other nitrogenous — sometimes also called plastic — foods, being very 

 inferior flesh-formers themselves. Roots used as food are scarcely worthy 

 to be called nourishing food at all, but rather pleasant additions to a meat- 

 diet, because the percentage of water (upwards of 90) is so great that the 

 actual amount of nutritive matter contained in a portion eaten at a meal 

 is extremely small. The carbonaceous ingredients (especially sugar) are : 

 in carrots, 7*7 ; in parsnips, 13*7 ; in beet, 12*5 — the average amount of 

 albuminoids being only 0*7. They are useful, however, for their salts. 



Taking wheat as a type of a nearly perfect food, the grain consists of 

 a single seed, invested by the dry pericarp or ripened ovary, so that it is 

 really a complete fruit. There are five skins of one cell in thickness, 

 being the homologues of the pericarp and seed-skins combined. It was 

 thought that the outermost, the cells of which are elongated and of a 

 fibrous nature, was coated with silica, like the surface of a straw ; but 

 Professor A. H. Church analysed it, and detected none. He found, how- 

 ever, that, as far as any nutrition was concerned, the ash, 2*6 per cent., 

 contained only 15 '3 per cent, of phosphoric acid, while the high proportion 

 of fibre rendered it nearly valueless. Moreover, " decortication " * is also 

 desirable, as the tip of the grain carries bristly hairs, technically called 

 the " beard." One of the inner layers of the husk, called the " cigar 

 coat " from the shape of its cells, is coloured, and gives rise to the 

 varieties known as red, yellow, grey, white wheats, &c. Certain phos- 

 phates, &c, are contained by them, so that these inner skins should be, 

 and indeed always are, retained in whole and wheat meal. The most 

 important layer is that next within the innermost skin. It is the outer- 

 most part of the endosperm of the seed, or the tissue which contains the 

 reserve food for the use of the embryo or germ. This layer is called the 

 aleurone or cerealin layer. It consists of somewhat cubical cells filled 

 with albuminoid grains, accompanied by the ferment cerealin, the 

 function of this ingredient being to digest the aleurone on germination 

 by converting it into soluble peptones. The rest of the endosperm consists 



* A word used by millers, who, in high-class milling, remove this outermost skin 

 before grinding. 



